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Title: Initiative in Evolution
Author: Kidd, Walter
Language: English
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Transcriber’s notes:
The text of this book has been preserved as in the original except
for correction of some typographic errors (see below) and punctuation
inconsistencies. Italic text is denoted by _underscores_ and a caret
mark ^ precedes any superscripted character(s). Footnotes have been
numbered and positioned below the relevant paragraphs, and some
illustration captions have been moved closer to the relevant text.
Corrected misspellings include the following:
constitutent —> constituent
It —> If
o —> to
endotheliun —> endothelium
ecomomy —> economy
involutary —> involuntary
old factory —> olfactory
tacile —> tactile
irrevelant —> irrelevant
tranverse —> transverse
decebrate —> decerebrate
Thistleton —> Thiselton
opprobious —> opprobrious
Duputryen's —> Dupuytren's
ditēthēsis —> diēthēsis
INITIATIVE IN
EVOLUTION
BY
WALTER KIDD, M.D., F.R.S.E.
AUTHOR OF
“USE--INHERITANCE,” “DIRECTION OF HAIR IN ANIMALS AND MAN,”
“THE SENSE OF TOUCH IN MAMMALS AND BIRDS,” ETC.
_WITH NUMEROUS ILLUSTRATIONS_
H. F. & G. WITHERBY
326 HIGH HOLBORN, LONDON
1920
PREFACE.
The Great War imposed on speculative biology a moratorium as in the
long vacation of lawyers, in which are causes left over to the next
term. And so the old case Lamarck _versus_ Weismann was not heard in
the Courts of Science during the war. In the present term it is due to
be heard afresh, and at some future date to come up for settlement.
The chapters that follow comprise some of the pleadings on behalf of
the plaintiff and are part of the brief of a junior counsel. This
adjective, alas! signifies not the years--for such are often old enough
to be the fathers of the leaders--but the standing and attainments of
a junior. But in the open Court of Science, and on suited occasions,
it may be the business of a junior to question, in the interests of
his client, the authority even of Attorneys-General and Lords Chief
Justice. In matters of thought and inquiry it is useless to retreat
within a stronghold and bar the gates. It may be satisfactory to
himself for one Milner to write a book on behalf of a certain body of
doctrine and call it _The End of Controversy_, but the book should
have held the sub-title _The End of Progress_. The Newtons, Pasteurs
and Darwins have seldom wielded the weapon of controversy, though the
triumph of _The Origin of Species_ would have been slower without the
aid of Darwin’s brilliant champion and candid friend. But, if the
leaders seldom need such help, for the Gibeonite it is a matter of
course and simple necessity. With all the urbanity due to the great
subject-matter should this pleasant duty be performed. Who would not
prefer to the fierce Spaniard the genial Portuguese, discussing all
subjects without rancour, and lover of bull-fights though he be, taking
care to wrap in cork the horns of his fighting bulls?
The earlier chapters treat of the arrangement of the mammalian hair,
which has occupied my attention for over twenty years, and this
has led straight to the other subjects, because of their bearing on
Lamarckism and Initiative in Evolution. The tentative conclusions
reached years ago have been strengthened by further knowledge and
reflection, and perhaps by certain criticisms. The furrow ploughed
may have been lonely, but the pursuit has not been without the mild
pleasure of seeing fresh scattered portions of the field coming into
their natural order. The resulting state of mind resembles that of
a certain Mr. Burke recorded in the annals of a golf club, second
to none, the Ancient, and now Royal Blackheath, among whose minutes
appears the following:--
“20th September, 1834.
Present, Mr. Burke, _Solus_.
The dinner was good, wine abundant, and the utmost harmony prevailed.
The want of grouse was severely felt this day.”
It is written on page 101 of the _Chronicles of Blackheath Golfers_.
My debt to such writings as those of Professors Arthur Keith, Woods
Jones, Graham Kerr, and Professors Sherrington, Starling, Schäfer,
McDougall and Ward is too obvious to the reader to need more than a
bare mention.
I have to thank one critic, Miss Inez Whipple, now Mrs. H. Wilder
Harris, for her able if hostile criticism of two former books of mine
which has been of use in this one; and Mr. R. E. Holding for good help
extending over many years in the preparation of the illustrations, and
for many a good suggestion.
W.K.
CONTENTS.
CHAPTER PAGE
I.--From Known to Unknown 1
II.--Review of the Position 8
III.--The Problems Presented 22
IV.--Initial Variations and Total Experience 30
V.--Method of Proof 36
VI.--Evidence from Arrangement of Hair 39
VII.--The Evolution of Patterns of Hair 50
VIII.--Can Muscular Action change the Direction
of Hair in the Individual? 64
IX.--Habits and Hair of Ungulates 74
X.--Habits and Hair of Ungulates 86
XI.--Habits and Hair of Carnivores 92
XII.--Habits and Hair of Carnivores 98
XIII.--Habits and Hair of Primates 103
XIV.--Miscellaneous Examples 115
XV.--Experimental 124
XVI.--First Summary 140
XVII.--Varieties of Epidermis 145
XVIII.--Arrangement of the Papillary Ridges 157
XIX.--Flexures of the Palm and Sole 170
XX.--The Evolution of a Bursa 178
XXI.--The Plantar Arch 192
XXII.--Muscles 200
XXIII.--Innervation of the Human Skin 218
XXIV.--The Building of Reflex Arcs 231
SUMMARY 257
INDEX 259
LIST OF ILLUSTRATIONS.
FIG. PAGE
1 Arrangement of hair on the forearm 42
2 Diagrams of hair-patterns 51
3, 4, 5 Neck of horse, showing muscles and tendons 53, 54
6–19 Side of neck of various horses, showing
varieties of hair-patterns 56–62
20–29 Illustrations of human eyebrows, showing
muscular action and hair-direction 70–73
30 Front view of horse, showing pectoral pattern 76
31 Side view of horse showing hair-direction 77
32, 32a Frontal region of horses, showing muscles and
hair-pattern 78
33 Side view of horse, showing chief superficial
muscles 79
34, 35 Side and back views of cow, showing
hair-patterns on back 88
36 Lioness, showing direction of hair-streams on
muzzle 93
37 Back of lion, showing hair-pattern 95
38–40 Gluteal region, foreleg and chest of
domestic dog, showing hair-direction 99, 101
41 Arrangement of hair on back of lemur,
chimpanzee and man 105
42 _Idem_ chest 109
43 Giraffe, showing hair-patterns of neck 116
44 Giraffe in attitude of drinking or browsing
off the ground 117
45 Bongo, showing hair-patterns of chest 119
46 Kiang. Side view showing inguinal and
axillary patterns 121
47 Forefoot of llama, showing hair-direction 122
48 Two-toed sloth, showing action of gravity
on hair 123
49 Domestic horse, fully harnessed 128
50 Side view of domestic horse, showing
reversed hair due to harness 129
51–58 Necks of various horses, showing reversed
hair due to collar 132–135
59 Right hand, drawing of papillary ridges,
made from impressions 158
60 Right foot. _Idem_ 160
61–70 Hands and feet of lower animals,
showing papillary ridges 161, 163–166, 168
71 Flexures on palm of right hand.
Drawing made from impression 171
72–79 Flexures on hands and feet of various
lower animals 172–175
80 Drawing of flexures of sole of foot of man,
young adult 176
CHAPTER I.
FROM KNOWN TO UNKNOWN
Upward--still upward--still upward to the highest! Such is the claim
of modern man for the story of himself and the lower inhabitants of
the globe. The zoologists have gone so far as to confer upon him the
surname Sapiens--Homo Sapiens. Learned indeed he is, and heir of all
the ages, but whether or not his assumed surname be warranted the
doctrine of descent with modification can never again be questioned.
The work of Darwin was crowned when he compelled a general acceptance
of that doctrine, and now the Descent of Man and the Ascent of Man
are equivalent terms for a natural process which has converted man
from a thing to a person, and is the foundation of all modern thought.
The biologist works secure in the knowledge that he is studying some
portion of a chain of life stretching back for incalculable ages, and
is not careful to produce those missing links demanded by the once
formidable foes of his fundamental principle. Haeckel may announce that
Pithecanthropus Erectus of Dubois is truly a Pliocene remainder of that
famous group of highest Catarrhines which were the immediate pithecoid
ancestors of man. This may or may not be true, but if true it makes
the descent of man from a lower stock none the surer, the increasing
verification of which is not found to rest on missing links.
Many of the discoveries of modern science are made by proceeding from
known phenomena to the unknown, or, more precisely, from the well-known
through the little-known to the hitherto unknown.
As to the validity of knowledge it is enough to say this--and pass
on--_all our knowledge is provisional and imperfect, and much of our
ignorance is as transient as ourselves_.
There are two chief ways in which historians deal with their
subject-matter, though the moderns combine them. When oral tradition
gives place to written records the lineal descendant of the bards
and annalists collects his scanty authorities and compiles his story
from them from beginning to end. The Anglo-Saxon Chronicle of Bede
and Alfred, the Book of Howth, the works of Giraldus Cambrensis, the
Chronicles of Froissart and the Memoirs of de Comines were composed
in the only way that was then possible. But the muse of history
entered on a deeper and more fruitful course when about ninety years
ago the study of documents became an essential feature of historical
work. It was then that the historian grew up, entered upon his finest
inheritance and assumed his Greek title, Enquirer, Student of facts,
Man of research. He is now nothing if not a man of science as well as
of letters. With a wealth of documents within his reach so great that
the 3239 Vatican cases full of them formed by no means the richest
collection in the archives of Europe, he proceeds to read backwards
correctly what many an earlier annalist read forwards falsely. “We
are still at the beginning of the documentary age which is destined
to make history independent of historians, to develop learning at the
expense of writing, and to accomplish a revolution in other sciences as
well.”[1]
[1] Acton. _A Lecture on the Study of History_, p. 19.
The Historian a Biologist.
It is not too much to say that he who studies history, national,
political, constitutional, ecclesiastical, military or economic is as
much a biologist in the widest sense as the botanist and zoologist.
Indeed these were till recently termed students of natural _history_,
until the advance of knowledge gave us the various special groups of
workers, conveniently called biologists. Though the study of human
history by documents is an essential part of the historical method
and the student may read _his_ subject backwards, this would not of
itself warrant the technical biologist in doing so, even though he be
a child of Nature and part of her--“Nature’s insurgent son.” But some
reflection on the facts of certain provinces of science affords ample
justification for the method. It is chiefly in questions of origin
that it avails, while it fails in that form of research by experiment
which is the glory of modern science. A few examples of the process of
passing from the known to the unknown will illustrate the method.
Darwin.
Much of the _Origin of Species_ and all of the _Descent of Man_ was
founded on this method; thus in the former the conceptions of struggle
took their main rise from the work of Malthus on Human Population, and
of variation from domesticated animals and plants, and this is true
also of Wallace. A mere glance at the divisions of _The Descent of Man_
shows that it could never have been attempted in any other than the
backward way.
Geology.
In their researches on the crust of the earth Playfair, Hutton and
Lyell did not pursue them by going down a coal mine till they came to
the lowest available beds and work upward from these to the highest.
Though for purposes of exposition a great geologist, as Sir Archibald
Geikie, may expound the making of the earth from the lowest to the
highest levels, and Professor Bonney tell us the _Story of our Planet_
from beginning to end as if he had watched it unfolding, Lyell in his
_Principles of Geology_ shows how the studies of his great province
began. There we have the backward reading of its story pursued by
himself and other great ones, and where it led them. Commencing with
the Pleistocene period and passing through Neocene and Eocene periods
through the Mesozoic Era and its cretaceous, jurassic and triassic
systems to the Newer Palæozoic Era and its Permian, carboniferous, and
Devonian systems, the older Palæozoic Era and its Silurian Ordovician
and Cambrian systems, he reaches the unknown. But before all this
patient research and its record is reached he treats, as he must, of
consolidation and alteration of strata, of petrification of organic
remains, elevation of strata, horizontal and inclined stratification,
of faulting, denudation, upheaval and subsidence as they combine
to remodel the earth’s crust. The title of his classical work is
significant--_An Attempt to Explain the Former Changes of the Earth’s
Surface by Reference to Causes now in Operation_ (it may be noted that
in 1830 they were fond of capital letters and of underlining their
words). If these great men had been condemned to the sole use of the
method of the annalist in his treatment of human history, that of the
coal mine in geology, this great province of knowledge would never have
been what it is to-day.
At this point I think it well to state that this illuminating principle
of Lyell is pursued in nearly all the matters of fact and their
interpretation contained in the following chapters, so that from time
to time I shall have to employ the verb, coined for the purpose, when I
attempt to “Lyell” them on behalf of Lamarck.
Anthropology.
The anthropologist could hardly make a start with his research, if,
knowing nothing of his own anatomy, physiology, customs and beliefs, he
tried to interpret the physical features, habits, manners, customs and
rites of an African tribe. Without such prior knowledge he would find
it a profitless task to journey to the banks of the Zambesi and bring
back any intelligible history of the aborigines. If he did not know the
games of a European child how could he understand the variants of them
such as the writer of _Savage Childhood_[2] expounds so well?
[2] _Savage Childhood_, Dudley Kidd.
The Sources of Rivers.
To trace the course and source of a river is a simple task through the
work of modern geographers, and such a pursuit illustrates well the
two methods here considered, but it is doubtful if any river was ever
traced originally from its fountain head to its mouth. The backward
way of such exploration, from the nature of the case, has always been
taken, and men have traced the more or less finished products of the
lower stretches, backward, still backwards, even as in the Indus, to
the still-unknown. The earliest thinkers and seekers in the plains of
Bengal were familiar with much of their great sacred and composite
river as it flowed into its delta. Slowly, laboriously, here a little
and there a little, they learned its stupendous story. They found the
plateau of Tibet in the Himalayas where the twin-sisters, Brahmaputra
and Ganges were born, and saw how from the one high cradle they parted
on their eastward course for a thousand miles with the mountain-chain
between them, and how, coming together again, the one descending
through Assam and the other flowing through the plains, reinforced by
the Jumna, they united to form the Ganges-Brahmaputra. A great subject
indeed for the early geographer, but one which he could only follow in
the backward way. Again how well known and revered in Egypt was the
Nile for thousands of years before its source in Victoria Nyanza could
be traced, even though Nero might send his explorers as far as the
marshes of the White Nile, and Ptolemy’s search for it might lead him
to guess the riddle, and assign it to two great lakes!
Genealogy.
Not many of us can trace our ancestry in the direct male line to
the 8th century by authentic and written documents as did a Hebrew
friend of mine, thus effectually meeting the doubts of a prospective
brother-in-law who asked him as to his fitness to enter a family which
was able to produce a stray peer of the realm in its roll. On the other
hand a man who has lost his parents in childhood may know nothing of
them but that his father’s name was A. Mann, and that he was buried
in a Kentish churchyard. He may go on a pilgrimage and find there
recorded the fact that A. Mann was the son of A. Mann, Gent, who came
from Northumberland. He will doubtless make another pilgrimage and find
there a large vault, and over it an imposing record of many a Mann,
and yet further he may go, and from the Heralds’ College find out the
still earlier derivation of his ancestors.
Detection of a Crime.
There are two chief ways of detecting a crime. By oral evidence from
eye-witnesses or confession of the accused you may get direct proof,
though even here are pitfalls from careless and hasty witnesses on the
one hand, or on the other from a strange perversion of mind of the
confessing person which is well enough known to forensic medicine.
You may thus bring home to the accused his guilt by the method of
the annalist. Or you may employ the more common method of studying
circumstantial evidence; the story of the crime is read backwards and
a verdict of guilty is given. This is the main stuff of which the
prevalent detective story is composed.
A Parable.
A plain parable may well conclude this chapter.
As I mused on the chain of life I found a piece of whipcord which had
been lying by for twenty-five years since some of it was used for
rigging a model yacht, and this very efficient product of human art
seemed to speak to me on the subject of my musings. Perhaps if Huxley
could extract from a piece of chalk or lumps of coal two magnificent
expositions on geology and biology, this little trifle of cord might
afford a text on a way of looking at living things which should be
useful in this old case of Lamarck _v._ Weismann--and others.
Should I learn the story of the whipcord forwards like an annalist,
or backward like a modern historian? Clearly it could be done in a
measure by either method. Here was a highly finished product of which
either might furnish the story, and of which, we may suppose, I knew
nothing. I tried the backward way, and by the aid of a needle began
to unravel it. The cord was as good as if just made, slender, strong,
twisted, with some glazing on the twisted threads. It showed three
main bundles, and each of these was composed of two smaller ones.
The substance of all these six was found when examined with a lens
to consist of minute silky fibres varying from a quarter of an inch
to an inch in length. This was all I could learn without a stronger
magnifying power or a chemical analysis, and the direct search was at
an end. I gathered since then that the first three bundles were called
“strands,” and the two composing each of these “yarns,” and that the
fibres were from a plant called hemp. This did not carry the story
deep or far, and illustrates how often in the backward method facts
have to be supplemented by inference. But I had learnt some undoubted
facts and some inferences from them nearly as certain. Some mind of
man had conceived and hands carried out the division of the bundles of
fibres into three strands, had twisted them somehow so as to reduce
their length by a quarter and yet not far enough to rupture them, and
had thus fitted them the better for their purpose by a reinforcement
of tensile strength due to the twisting. I could also see that this
same mind had seen it better to divide each of these strands into two
yarns before the final twisting, and that in framing the yarns the
silky fibres of the plant had been squeezed together by some powerful
agency and yet not disintegrated, and that the finished product had
been immersed in a protective substance which gave it a slight glaze.
In short, I, though a child in these matters, read much of the story
of this cord in terms of mind dealing with given organic matter. I may
add that I did not imagine myself a little Paley, and that I do not
intend to “take in” the reader as to the argument from design and final
causes, even though this parable may feebly resemble Paley’s study of
a watch. The conclusion was perfectly clear that certain directing
grey cells of a certain brain had interfered with and acted upon some
plastic vegetable matter, and one could at the “strand” stage, the
“yarn” stage, and the “fibre” stage see mind writ large.
The Forward Way.
The limits of the former method are obvious, but I might also attempt
to follow the little story as a crime is followed and described by
eye-witnesses. So I go to an old-fashioned rope-factory and ask the
foreman questions about the making of twine, cords, ropes and cables.
He shows me bundles of hemp; he calls them Russian, Italian or
American, and goes on to tell me how the fibre is “heckled” or combed,
how “tow” is separated from “line,” and how the yarns are pressed
together and twisted, how they are at first rough and bristly, and are
then dressed, polished, and “sized” with such a starch as that of the
potato. When I proceed to ask him about the plant itself his interest
flags, and he becomes vague. He says, “You had better ask the Head,
young Mr. X., he knows these things better.” I find the Head with his
golf clubs over his shoulder and about to start on his “business,” and
he is polite, but says he knows very little about the origin of his
hemp. “You should go over the way and ask Messrs. Y. if they will let
you see the expert who advises them in their business, he will know.”
The expert is at home and kindly and fully describes to me the early
home of the wild _Cannabis Sativa_ in a moderate climate of Asia, the
rich soil it needs for its growth and the various countries of the
world into which it has been introduced; and the bast-fibres of the
bark of this plant which from remote antiquity has supplied the silky
stuff. He then tells me how the stems are dried and crushed, and then
of the important stage of fermentation or “retting” in water, how they
are again beaten in a “break,” then rubbed and “scutched,” and finally
“heckled” or combed; and, as to analytic chemistry, he tells me that
the chief constituent is cellulose. This quest is now over and I know
much I could not find out by the backward method, though the dependence
of its rival upon the presence of honest and capable eye-witnesses
is not less obvious. It is not alone in ecclesiastical history that
cheats and forgers of documents exist. In the world of Nature there
may be, for all we know, biological False Decretals that may lead
us far astray, such perhaps as Amphioxous and Archæopteryx, and the
Pseudo-Isidore who produced them may yet be discovered.
CHAPTER II.
REVIEW OF THE POSITION
The modern story of the theory of organic evolution shows certain
important dates--1859, 1880, 1894, 1895, 1899 and 1909. These begin
with the _Origin of Species_ and end with the publication of a volume
in commemoration of its jubilee, when most of the leading students of
evolution united to render homage to Darwin. The year 1859 has been so
often and so worthily treated that it is enough here to say that the
fifty years between the issue of the work of Darwin and Wallace and
1909 saw a greater revolution in biology, speculative and practical,
than any period so relatively brief had ever seen.
In the year 1880 the “coming of age” of the _Origin of Species_ was
celebrated. On the 9th of April at the Royal Institution an address
was given by the powerful friend, champion and candid critic of
Darwin, and before the scientific and educated world Huxley was able
to say with his own force and directness: “Evolution is no longer an
hypothesis, but an historical fact.” It may be noted in passing that
Darwin’s theory of natural selection is not referred to in the address.
Challenges and opposition from various quarters met this confident
claim of the formidable speaker, as doubtless he desired, but the work
of the succeeding half-century has done little or nothing that does
not establish that claim. It is hardly to be doubted that if in the
jubilee-year, 1909, Huxley had been alive on this earth, instead of
elsewhere, his eloquent voice would have been heard to declare with
emphasis equal to that of 1880: “Selection is no longer an hypothesis,
but an historical fact.” Some such statement, with the _imprimatur_ of
a great name would have removed from the jubilee-volume that slight
aspect as of a Dutch chorus[3] which is apparent in it. A remark of
Kelvin’s when he was conferring a medal of the Royal Society on Huxley
may illustrate what has been said above. He said that they must all be
thankful to have still among them that champion of Evolution who once
bore down its enemies, but was now possibly needed to save it from its
friends. It may be regretted that it was not so in 1909.
[3] The above remark as to the jubilee-volume needs to be explained
and justified. In it there is an important essay on each of the great
provinces of Weismann, Mendel and de Vries, and in each of these the
highest living exponent speaks, Professors Weismann, Bateson and de
Vries. Bateson expresses admiration for Weismann’s destructive work,
but shows plainly that he holds it to have failed in its fundamental
purpose. Nevertheless, by a neat _tour d’addresse_ he adopts
Weismann’s uncompromising attitude on the inheritance of acquired
characters, which happens to agree exceedingly well with his own
scheme. He has but one insignificant reference to de Vries on p. 95
where he finds help for his doctrine.
Weismann makes no reference to Mendel or de Vries. De Vries makes
none to Weismann or Mendel, but without stating it in his essay he
is known to be in opposition to Weismann’s dogma on the inheritance
of acquired characters. These three eminent biologists would
thus seem to have worked on diverging lines. The two first agree
heartily, Weismann explicitly and Bateson by implication, as to the
forbidden doctrine, “on the ground that it closes the way to deeper
insight”--in other words their mutually destructive theories. So it
stands thus in the book--Weismann throws over Lamarck, Mendel and de
Vries; Bateson throws over Weismann (as again in 1914) and de Vries;
de Vries ignores Weismann and Mendel.
Dr. Lock in his book on Variation, Heredity and Evolution, 1906,
says that Weismann practically ignores the evidence of Mendelism in
heredity, and adds, p. 261, “But at the next step the Mendelian parts
company with Weismann.”
One cannot avoid noticing, incidentally, that the vast mass of work
of the biometricians led by Galton, Weldon and Professor Karl Pearson
is conspicuously absent from the book. Prof. J. Arthur Thomson says
that there should be no opposition between Mendelian and Galtonian
formulæ, “they are correlated, and ultimately they will be seen in
complete harmony as different aspects of the same phenomena. But it
is simply muddleheadedness which can find any opposition between a
statistical formula applicable to averages of successive generations
breeding freely, and a physiological formula applicable to particular
sets of cases where parents with contrasted dominant and recessive
characters are crossed and their hybrid offspring are inbred.”(a)
concerning which see the Preface to Bateson’s _Mendel’s Principles of
Heredity_, 1902, with remarks on some of the Galtonians.
(a) _Heredity_, p. 374.
Considering the mole-like and persistent work of the biometricians,
some who are at present keeping well-ordered lawns may find some
day a few disturbing heaps of facts. I am reminded here of an
historic duel, Oxford _v._ Cambridge, which took place soon after
the introduction of Mendel’s discoveries into England at the London
Zoological Society, when Prof. Bateson expounded them with enthusiasm
and when Weldon repelled them with cogent and incisive arguments.
The duel lasted nearly two hours and that was not too long for the
audience, but one has the impression that some of what Professor
Thomson calls muddleheadedness must have been somewhere existing.
However, the duel was fought when Mendelism was young.
Three Blows to Darwin.
But other historic events are more relevant to my immediate purpose
than these.
Three blows were delivered against Darwinism in the years 1894, 1895
and 1899 by Prof. Bateson, Weismann, and again Prof. Bateson, under
which it seemed to reel, but from which it is more than likely it has
derived but greater strength.
BATESON.
In 1894 Prof. Bateson published his large and important work,
_Materials for the Study of Variation_. As a distinguished student
and teacher of biology he found the received doctrine of evolution
in straits as regards the factor of natural selection in producing
specific differences, as indeed happened to another equally eminent man
during the next year. He was profoundly discontented as to the origin
of specific differences on the theory of direct utility of variations,
and he said “on our present knowledge the matter is talked out.”[4]
He threw over the study of adaptation “as a means of directly solving
the problem of species.” He came to the conclusion “Variation is
Evolution,” and affirmed that the readiest way of solving the problem
of evolution is to study the facts of variation. Hence arose this
notable book, and hence one of his trenchant statements to the effect
“that the existence of new forms having from their beginning more or
less of the kind of perfection that we associate with normality, is a
fact that once and for all disposes of the attempt to interpret all
perfection and definiteness of form as the work of selection,”[5]
and “Inquiry into the causes of variation is as yet, in my judgment,
premature.”[6] It will hardly be denied that a work which contained
such statements as these from such a source seemed momentous in its
influence on the fate of Darwin’s theory. Prof. Bateson yielded to
none in his loyalty to Darwin, as far as he knew himself, and here he
is as candid as Huxley, and he declares that in his treatment of the
phenomena of variation is found nothing which is in any way opposed
to Darwin’s theory. The shade of Darwin might nevertheless have
looked with some misgiving at this man over against him with a drawn
sword in his hand, and have asked gently, “Art thou for us or for our
adversaries?” Prof. Bateson’s work chiefly requires to be considered
here because to any reader of it there must come the conviction on
the one hand of Prof. Bateson’s merits and power, and on the other of
his limitation as a student of organic evolution. In 1894 is evident
already an exclusive attention to structure rather than function,
to anatomy than physiology; the anatomical leaven in doctrine has
leavened the whole lump. For him physiology of animals and plants does
not exist, or at the best is the outcome of structures which arise
through variation and selection. This, if I may say so, is as much his
strength as his weakness. There have been other great biologists, such
as Geoffrey Saint-Hilaire and Richard Owen, of whom this is true. If
that were all one would not wish the reader to be troubled with any
criticism of one’s betters, indeed such remarks as are here made do not
amount to criticism at all, but just plain text-book statements. It is
also evident that the outlook of Prof. Bateson was being prepared for
a revelation which had not yet come, in which he took a prominent, if
not dominant part, I mean the great rediscovery of Mendel’s work by
de Vries, Correns and Tschermak and himself in England. His keen and
close attention to anatomical structures was preparing his mind for the
germinal conceptions of unit-characters, dominance and segregation.
The intensive cultivation of the fertile field of genetics proceeded
apace, and Prof. Bateson in his contribution to the jubilee-volume of
1909 betrayed the trend of his devotion to a system of _distribution_
rather than formation of the qualities of an organism. The organism as
an historical functioning, striving being, had receded once for all
from his vision. He hazarded the suggestion in _Heredity and Variation
in Modern Lights_ that “variation consists largely in the unpacking
and repacking of an original complexity,” and that “it is not so
certain as we might like to think that the order of these events is not
predetermined.” Incidentally one may remark that, _malgré lui_, Prof.
Bateson stands forth as a modern Paley as does Weismann in his great
rival and opposing scheme. It is true that he says “I see no ground
whatever for holding such a view, but in fairness the possibility
should not be forgotten and in the light of modern research it scarcely
looks so absurdly improbable as before.” Having drawn the sword he
threw away the scabbard in 1914 when he occupied the presidential chair
of the British Association of Science at Melbourne and Sydney. He had
said in 1894 in his book on variation as stated before, “Inquiry into
the causes of variation is as yet, in my opinion, premature,” and
then in 1914 at Melbourne, after twenty more years of study of the
subject in the Mendelian direction, “It is likely that the occurrence
of these variations is wholly irregular, and as to their causation _we
are absolutely without surmise or even plausible speculation_.” (my
italics).[7] So, on this fundamental point, he stands where he did when
he began the study of variation, but apart from this point he again
threw out his suggestion of 1909 as to the unpacking and repacking of
an original complexity. At Melbourne he said, “Lotsy has lately with
great courage suggested to us that all variation may be due to such
crossing. I do not disguise my sympathy with this effort.”[8] _All
variation!_ He said later, “In spite of seeming perversity, therefore,
we have to admit that there is no evolutionary change which in the
present state of our knowledge we can positively declare _not due to
loss_.”[9] (Italics mine.) These two statements of 1914 are enough to
show that the biologist of 1894, 1899, 1909 and 1914 has evolved in
a definite line, and it is to his honour that he has remembered “to
thine ownself be true.” But he is not so true to himself in his scorn
of those who propound theories. For myself I would give little for
the biologist who did not hold or propound some theory. What was the
penultimate and stirring message of the gifted G. B. Howes? “We live
by ideas, we advance by a knowledge of the facts.” The self-denying
ordinance affirmed and reaffirmed by Prof. Bateson is not observed
even in the Melbourne and Sydney addresses. In the former, he says
“at first it may seem rank absurdity to suppose that the primordial
form or forms of protoplasm could have contained complexity enough to
produce the divers types of life,” and asks us to open our minds to
this possibility. Again “I have confidence that the artistic gifts of
mankind will prove to be due not to something added to the makeup of an
ordinary man, but to the absence of factors which in the normal person
inhibit the development of these gifts.” And at Sydney, “Ages before
written history began, in some unknown place, plants, or more likely a
plant of wheat lost the dominant factor to which this brittleness is
due, and the recessive thrashable wheat resulted. Some man noticed this
wonderful novelty, and it has been disseminated over the earth. The
original variation may well have occurred once only in a single germ,”
and “so must it have been with man.”[10]
[4] _Materials for the Study of Variation_, p. 5.
[5] _Op, cit._, p. 568.
[6] _Op. cit._, p. 78.
[7] _Nature_, 1914.
[8] _Op. cit._, Aug. 20th and Aug. 27th, 1914.
[9] _Nature_, 1914.
[10] _Op. cit._, 1914.
These are three stupendous stretches of imagination and theory in one
address, which would have been the poorer if they had not overcome
the accomplished speaker’s dislike of the theories--of others. If
they are not ideal constructions of a high order I do not know the
meaning of that term. They are worthy of Weismann the Prince of ideal
constructionists. Prof. Bateson might indeed be another Newton with his
_Hypotheses non fingo_.
Turning to another important biological doctrine one can see what it
may be legitimate to call a bi-phyletic parallelism in the biological
make-up of Prof. Bateson. Again is seen consistency of view and loyalty
to his first love. Two references from these addresses will be enough
to introduce the point.
At Melbourne, “We thus reach the essential principle that an organism
cannot pass on to offspring a factor which it did not itself receive in
fertilization.”[11]
[11] _Op. cit._, 1914.
At Sydney, “The factors which the individual receives from his
parents, and no others, are those which he can transmit to his
offspring”[12]--in other words the doctrine of the inheritance of
acquired characters is estopped. As to this he speaks in 1909 more
doubtfully on p. 90 and on p. 95 almost dogmatically.[13] There is just
a convenient haziness of meaning in the term “factor” with which some
play might be made, but, taking it to mean what the context indicates,
an acquirement made by the individual during its personal life, we have
pretty clear evidence that Prof. Bateson will have nothing to do with
the inheritance of acquired characters as that doctrine is understood
by the unsophisticated biologist. This opposition should be counted
unto him for righteousness rather than the reverse, for it falls into
line with his life’s work to which he has given of his best.--_Vestigia
nulla retrorsum._ The point reached here which concerns my purpose is
that the orthodox Mendelian still knows nothing of the cause or origin
of variation, and will have none of Lamarck.
[12] _Nature_, 1914.
[13] _Darwin and Modern Science._
This consideration of Prof. Bateson’s work of a quarter of a century
has been necessary for showing how the work of Weismann and himself
diverge gravely and yet meet at one point, and the year 1899, being
linked with 1894, has been taken out of its chronological order.
It may be permitted perhaps to say respectfully to the Mendelians in
the words of the dying father in the fable, “Dig, my sons, dig in the
vineyard.” If they follow still the course of the sons they may find
more gold than they have found already and perchance that which is
better than gold. But they will produce from it nothing that is not
there.
Two Parables.
Here gentle reader (I seem to remember this style of address in
the stories of our youth) pause with me in a little oasis of the
desert-stage of our journey, and brush off some of the dust, while I
briefly narrate two incidents, but I pray you also not to leave me in
the midst of them so that you may escape the next short stage.
A traveller, small and insignificant, armed only with an oak cudgel,
was passing alone through a South American forest. As he trudged
forward he noticed at a certain point in the path (shall we call it
1894–1899?) that a jaguar was watching him and was about to break his
truce with man. He turned off to the right and there he saw a puma
and this too seemed to meditate evil. He hastened forward just in
time as his two enemies sprang at him, and these two near relatives
were locked in mortal grip--and so he passed on safe!
The reader, naturalist or layman, can point the moral for himself.
At the battle of Trafalgar, while fighting was in full progress on
one of the ships, some sailors were occupied in throwing overboard
the bodies of those who had been killed. A poor Scotchman badly
wounded and hardly conscious was taken up by two seamen, an
Englishman and an Irishman, and as they were about to throw him
overboard his feeble voice was heard to say “I’m no deed yet.”
“What’s that?” said the Irishman. “I’m no deed yet”; “Arrah, the
doctor said he was dead, over wid him,” said the Irishman.
Weismann.
During the period 1894–1899 there was a dramatic proclamation on the
part of one of the greatest living biologists, which was, in the cosmos
of biology, what the Proclamation of the Empress-Queen of India was in
1876, and it is not out of place to remind the reader that the fates
of the two Imperial utterances have been somewhat different. In 1895
Weismann issued his official statement of doctrine which was to crown
the work of his life, an essay on Germinal Selection. From Freyburg
in November, 1895, he wrote a preface to his address delivered on
September 16th in that year to the International Congress of Zoologists
at Leyden. This formed an epoch in biological thought and there lived
none so well qualified as Weismann to stand forth as its interpreter.
The well-translated, forcible language, and lucid thought leave the
reader in no manner of doubt as to his meaning. It took a wider form
in his final book on the Evolution Theory, but the germinal and
essential thoughts of the latter were contained in the former. From
1895 onwards the praise of Weismann was in all the churches. Probably
no modern worker in the fields of heredity and evolution has done so
much as Weismann towards raising great issues and removing some ancient
misconceptions; but it is one thing to raise great issues and another
to solve them. In this he has signally failed, nevertheless biological
theory would be the poorer if he had not made the attempt. Reflection,
the work of other biologists, and the remorseless hand of time have
shaken the edifices then raised. I will here only bring forward a few
of the most illuminating passages of the 1895 essay, and then refer to
the handling of Weismann’s work by Romanes.
This trenchant essay contains fifty-seven pages, of which reasoning
forms the greater part. As to the facts it might well pass for an
essay from Professor Poulton’s pen, for Weismann’s special province
of insects occupies nearly all the evidence from facts. Outside this
highly specialised group there are exactly fifty-three lines, or one
and a half pages, which deal with other animal groups, and there are
four casual allusions to plants occupying twelve lines in all! In the
essay of 1909 on the Selection Theory this treatment of animated life
in the world is improved upon and thirteen out of its forty-seven pages
refer to animals outside his favourite group of insects. Such exclusive
dealing with these little things does not commend the reasoning, at any
rate to a neo-Lamarckian; such a circle is too select for him.
Weismann’s Twelve Points.
The most striking remarks from the 1895 essay on germinal selection
are:--
1. “The real aim of the present essay is to rehabilitate the principle
of selection. If I should succeed in reinstating this principle in its
imperilled rights, it would be a source of extreme satisfaction to
me.”[14]
[14] Preface to _Germinal Selection_, 1895, p. xii.
2. Speaking of the whole theory of selection he claimed to have
found a position “which is necessary to protect it against the many
doubts which gathered around it on all sides like so many lowering
thunder-clouds.”[15] And he speaks on page 26 of “the flood of
objections against the theory of selection touching its inability to
modify many parts at once.”
[15] p. 38.
Thus Weismann stood forth to defend the crumbling edifice of Darwinism
and threw his shining sword into the scales, a scientific Athanasius
“contending for our all.” Again is seen a friend of Darwin from another
camp than that of Mendel, whose support needs to be received with some
caution. _Toujours en vedette_ is a useful rule.
3. Speaking of adaptedness in animated nature he says, “We know of
only one natural principle of explanation for this fact--that of
selection.”[16]
[16] p. 43.
4. “Germinal selection is the last consequence of the application of
the principle of Malthus to living nature.”[17]
[17] p. 43.
5. “Without doubt the theory (Germinal Selection) requires that the
initial steps of a variation should also have selective value.”[18]
[18] p. 38.
6. “Something is still wanting in the theory of Darwin and Wallace
which it is obligatory on us to discover if we possibly can. We must
seek to discover why it happens that useful variations are always
present.”[19]
[19] p. 15.
7. “It is impossible to do without the assumption that the useful
variations are always present, or that _they always exist in
a sufficiently large number of individuals for the selective
process_.”[20]
[20] p. 14.
8. “_Some profound connexions must exist between the utility of a
variation and its actual appearance, or the direction of the variation
of a part must be determined by utility._”[21]
[21] p. 18.
9. That “germinal selection performs the same services for the
understanding of observed transformations ... that a heredity of
acquired characters would perform without rendering necessary so
_violent an assumption_!”[22] (Italics mine.)
[22] p. 40.
10. Weismann speaks warmly of Professor Lloyd Morgan for his caution
and calmness of judgment but complains of him that he “has not been
able to abandon completely the heredity of acquired characters.”[23]
[23] p. 56.
11. As to passive effects of environment, etc., he says “the Lamarckian
principle is here excluded _ab initio_.”[24]
[24] p. 11.
12. “It seems to me that a hypothesis of this kind (Lamarckism) has
performed its services and must be discarded the moment it is found to
be at hopeless variance with the facts.”[25]
[25] p. 17.
I have only to add here that several years ago I wrote to Weismann
drawing his attention to some facts I had observed which seemed to me
to be instances of use-inheritance, and I received a reply in polite
but brief and Prussian terms to the effect that the facts referred to
must be capable of some other interpretation, for _the machinery for
their transmission did not exist_.
Each of these twelve quotations from Weismann’s essay is important from
the present point of view, and shows how far neo-Darwinians are likely
to promote the greater glory of Darwin, and though more than a quarter
of a century elapsed between this essay and his death Weismann was not
the man to have repudiated any of these strong statements.
Lighthouse Value.
I hope at this point a small digression is not out of place in order
to introduce an aspect of Weismann’s work which is not usually
appreciated. A child is aware of the great and lesser lights that
rule the day and night, but for modern man these are not sufficient.
Accordingly he has invented from immemorial times his oil lamps,
rushlights, tallow and wax candles, gas and electric light for the
illumination of his streets and houses. Prehistoric man did not seem to
need them, as he thought. These useful examples of applied knowledge
were obviously brought into use for showing man better where he was
going and where to go, what he was doing and what he wished to see. I
hope this trite remark may be pardoned, for there is another form of
light which suits my purpose of illustrating the aspect of Weismannism
referred to above, that is the light of a lighthouse. The ancients in
their crude way saw the need for this and as far back as the days of
Ptolemy II. a tower to give light was erected on the island of Pharus,
off the Egyptian coast, and it was called a _pharos_. Man found it
necessary, as navigation and seafaring advanced, to use this principle
more and more, and on headland, sandbank and rugged coast has built
noble structures to aid the sailor in his dangerous course. The oldest
and finest of these in Great Britain is the Eddystone lighthouse, built
first in 1695 by Winstanley and finally by Smeaton in 1756–9. For what
reason is a lighthouse built and placed where it is? For the precisely
opposite reason to that of the domestic candle. While this shows you
where to go and how better to do your immediate business, a lighthouse
is for the main purpose of showing a mariner where he should _not go_.
It has no relation to adornment or pleasure. It does not invite you to
come in your vessel and admire it. It tells you to go away and avoid
the sunken rock or treacherous sands.
I submit here the suggestion with all deference, that the final work
of Weismann has lighthouse value of a high order, as to the _modus
operandi_ of evolution. His greatness as a biologist, his candour and
skill in dialectics, have built up a veritable lighthouse which may
usefully warn the seeker after the path of evolution that he must turn
elsewhere if he would not founder upon a reef of facts.
The two great contributions to evolutionary thought that Weismann has
made should be considered separately, the theory of germ-plasm and that
of evolution, though the latter seems to be the necessary outcome of
the former. But the truth of Weismann’s view of heredity does not of
necessity require the error of his theory of evolution.
Romanes on Weismann.
For this study the examination of Weismannism by Romanes published in
1893 is of great value. I need only refer here to the main conclusions
of that lucid and learned examination.
Weismann’s work on the germ-plasm in pursuance of a theory of heredity
is pronounced by Romanes to have remained up to 1893 substantially
unaltered, though largely added to in matters of detail, and at the
present time as far as I gather from a study of the more recent
literature this theory holds the field or at least a commanding
position in it.[26] Originally he held that the germ-plasm possessed
_perpetual_ continuity since the first origin of life, and _absolute_
stability since the first origin of sexual propagation, but he has
shown himself willing to surrender the first postulate, and has himself
altered the second. As it stands now it must be admitted that the
continuity of the germ-plasm is an interrupted continuity with the
appearance of every inherited change; the continuity is theoretical,
not actual, and the stability of the germ-plasm is not absolute but of
a high degree. We can thus see in the story of this original theory of
heredity the lighthouse value of the _pharos_ of Ptolemy II.
[26] Romanes, _Examination of Weismannism_, p. 115.
“It is doubtful if anything better as to Weismann’s theory of
heredity can be said to-day than Romanes said in 1893, and inasmuch
as these two latter or distinctive postulates are not needed for
Weismann’s theory of heredity, while they are both essential to his
theory of evolution, I cannot but regret that he should have thus
crippled the former by burdening it with the latter. Hence my object
throughout has been to display, as sharply as possible, the contrast
that is presented between the brass (“iron” preferably) and the clay
in the colossal figure which Weismann has constructed. Hence also
my emphatic dissent from his theory of evolution does not prevent
me from sincerely appreciating the great value which attaches to
his theory of heredity. And although I have not hesitated to say
that this theory is, in my opinion, incomplete; that it presents not
a few manifest inconsistencies, and even logical contradictions;
that the facts on which it is founded have always been facts of
general knowledge; that in all its main features it was present to
the mind of Darwin, and distinctly formulated by Galton; that in so
far as it has been constituted the basis of a more general theory
of organic evolution it has proved a failure; such considerations
in no way diminish my cordial recognition of the services which its
distinguished author has rendered to science by his speculations
upon these topics. For not only has he been successful in drawing
renewed and much more general attention to the important questions
touching the transmissibility of acquired characters, the causes of
variation, and so on; but even those parts of his system which have
proved untenable are not without such value as temporary scaffoldings
present in relation to permanent buildings. Therefore, if I have
appeared to play the _role_ of a hostile critic, this has been only
an expression of my desire to separate what seems to me the grain of
good science from the chaff of bad speculation.”
It is far otherwise with Weismann’s theory of evolution. Romanes shows
that with the removal of its essential postulate the absolute stability
of germ-plasm, Weismann’s theory of evolution falls to the ground. He
has indeed surrendered much in his later building, his second temple
of Solomon, and prominent among these was the claim that the only
causes of individual variation and of the origin of species in the
uni-cellular organisms are the Lamarckian factors, just as in the
multicellular _the only cause of these is natural selection_. Thus we
see standing at the critical date, 1892, the first Eddystone lighthouse
of Winstanley, a greater and more important structure than the old
pharos.
Germinal Selection.
It can hardly be doubted that one of the “thunderclouds” threatening
Darwinism, of which Weismann spoke in 1895, was this examination of
Weismannism by Romanes. As the case stood then some fresh strategy
was needed if victory for Darwin was to be won, at least so the great
leader said. It must be remembered that it was the _personal_ selection
of Darwin which was held to be in danger. Accordingly germinal
selection was brought forth and remained the basis of Weismann’s later
_Evolution Theory_ of 1904 and 1909. Romanes did not live to see or
assist in the disproof of this ambitious piece of work so that his
“examination” is so far incomplete.
The position of germinal selection is defined in Weismann’s statement
that “it is the adaptive requirement itself that produces the useful
direction of variation by means of selectional processes within the
germ.” Here it is in a nutshell. The theory itself is consistent,
and clearness has been added to the earlier evolution theory by the
claim that a struggle for nutriment occurs within the fertilised ovum
between the innumerable determinants of the different parts, so that
maintenance or victory over weaker determinants takes place. Thus we
have a survival of the fittest _in petto_ in the germ analogous to
that of the individual organisms as we see them. There is of course
a resemblance here to the cellular or histonal selection of Roux,
but his doctrines are not weighted with the intolerable dogma of the
non-inheritance of acquired characters. But ultimately this conception
of germinal selection has to come down and bow to the tribunal of
facts, and the remark of Weismann on Lamarckism which has been
already quoted, “It seems to me that an hypothesis of this kind has
performed its service and must be discarded the moment it is found
to be at hopeless variance with the facts,” confronts the consistent
Weismannian. And I venture to say here that germinal selection is
represented by the Eddystone lighthouse of 1756–9 erected by Smeaton.
The grounds for this statement are afforded by numerous facts and
experiments, to which in the later chapters I propose to add a few
fresh ones, and by a growing body of opinion and authority in favour of
Lamarckian factors in evolution.
Three “lighthouses” of this metaphorical sort have thus been afforded
by the work of Weismann, represented by the Pharos of old, Winstanley’s
Eddystone lighthouse and that of Smeaton.
Authority.
We have then Weismann and Professor Bateson definitely ranged against
the position taken in this volume as to a cause or origin or variation
and the inheritance of acquired characters. To these we must add the
great weight of Sir E. Ray Lankester’s opinion lately given in a reply
to Professor Adami that “it is very widely admitted (more correctly
“claimed”) that no case of the transmission of what are called acquired
characters from parent to offspring has been demonstrated in so far as
those higher animals and plants which multiply by means of specialised
egg-cells and sperm-cells are concerned.”
It is not necessary to mention more than these “three mighties” of the
biological world.
Many others such as Prof. J. Arthur Thomson and Prof. W. K. Brooks,
of Johns Hopkins University, are still unconvinced as to Lamarckian
factors and ask for more evidence, and they have many to support them
in their opinion and claim. There is often a tone of weariness, as well
as wariness in their remarks on the matter.
In favour of the neo-Lamarckian position, with which stands or falls
the suggested cause of variation, there is a growing body of opinion,
with the mention of which I conclude this review.
1. The accomplished writer of _Form and Function_, Mr. E. S. Russell,
says the theory of Lamarck “although it had little influence upon
biological thought during and for a long time after the lifetime of
its author, _is still at the present day a living and developing
doctrine_.”[27]
[27] p. 215.
2. Sir Francis Darwin from the Presidential Chair of the British
Association of Science in Dublin in 1908 proclaimed his adherence to
the mnemonic theory of heredity, foreshadowed by Samuel Butler and
inaugurated by Semon, a condition of which is that acquired characters
are inherited. This caused much stir in the camp of “our friends the
enemy.”
3. Observations and experiments at variance with germinal selection and
its negative presupposition have been rapidly accumulated from the work
of botanists and zoologists who were prepared to appeal to the tribunal
of natural processes; though Weismann and some of his followers, with
some reason, look upon the evidence from plants as a weak link in
the chain of evidence. Many of the observations and experiments are
well-known and only a mere mention of them need be made here, they are
such as Mr. J. T. Cunningham’s observations on the effect of light on
the under surface of flounders, Kammerer’s on the changes in the colour
of salamanders to surrounding objects, and others by him on certain
amphibia and reptiles especially _alytes_ held by Professor McBride
to be convincing, though the latter are to be repeated at the London
Zoological Society’s gardens and are therefore _sub judice_--others
on brine-shrimps, on the effects of change of food on bee-grubs and
tadpoles, and of the change of level of environments of certain
cereals--others by Henslow on plants which have never been refuted, and
many by the late Prince Kropotkin. The latter have appeared at length
in certain issues of the Nineteenth Century in September 1901, March
1912, October 1914, and the last in January 1919, and they deal both
with plants and animals, and are too numerous to be mentioned here
individually.
Again, Professor Dendy as President of the Zoological Section of
the British Association of Science in September, 1914, devoted most
of his address to the subject of Lamarckism and firmly claimed as a
necessary factor of evolution “the direct response of the organism to
environmental stimuli at all stages of development, whereby individual
adaptation is secured, and this individual adaptation must arise
again and again in each succeeding generation.” He also maintains
this position in several passages in his important work _Outlines of
Evolutionary Biology_ published in 1912.
A statement by Professor Bower, President of the Botanical section
of the British Association of Science in 1914 should also be noted:
“I share it (the doctrine in question) in whole or in part with many
botanists, with men who have lived their lives in the atmosphere of
observation and experiment found in large botanical gardens and not
least with a former President of the British Association, viz., Sir
Francis Darwin.”
Professor Adami, in 1917, published an original work called _Medical
Contributions to the Study of Evolution_ in which from his extensive
knowledge of the subject he deals with evidence of inheritance of
acquired characters in lowly organisms as well as higher animals from
the point of view of pathology.
Enough has been stated here to show that the dogma of Weismann or
Lamarckian factors in organic evolution, _quâ_ authority, has been in
poor case during recent years, and it remains for me now to add my
small quota of the authority of facts.
CHAPTER III.
THE PROBLEMS PRESENTED.
In his classical work on Heredity, Professor J. Arthur Thomson exhausts
the evidence on Lamarckism available then (1908) in a manner worthy of
the summing-up of an English judge. This is presented to the jury of
the biological world and they are still considering it. Their verdict
and his sentence are not yet delivered, and it may be they will still
be long delayed. One might almost use the words of Professor Bateson,
previously quoted, “on our present knowledge the matter is talked out.”
I will make one prophecy in this volume and predict that the fourth
edition of this work in 1930 will contain the verdict of the jury and
sentence of the distinguished judge to the effect that in the case
Lamarck _v._ Weismann the plaintiff has won. As in the Great War the
Old Contemptibles held their line with the utmost difficulty against
the disciplined hosts of the greatest army ever known till then, and
yet the latter found their First Battle of the Marne, so perchance it
may be in the present struggle.
I introduce this chapter with an important passage from the above work
on the _Logical position of the Argument_, in which the two possible
methods of establishing the affirmative position of Lamarck are given;
these are, first, actual experimental proof of transmission, and,
second, a collection of facts which cannot be interpreted without
the hypothesis of modification inheritance. The words are:[28] “_The
neo-Lamarckians have to show that the phenomena they adduce as
illustrations of modification-inheritance cannot be interpreted as the
results of selection operating on germinal variations. In order to do
this to the satisfaction of the other side, the neo-Lamarckians must
prove that the characters in question are outside the scope of natural
selection, that they are non-utilitarian and not correlated with any
useful characters--a manifestly difficult task. The neo-Darwinians, on
the other hand, have to prove that the phenomena in question cannot
be the results of modification-inheritance. And this is in most cases
impossible._”[29]
[28] _Heredity_, 1908, p. 240.
[29] I prefer to state the above passage rather than that on
page 179, which is as follows: “The precise question is this:
_Can a structural change in the body, induced by some change in
use or disuse, or by a change in surrounding influence, affect
the germ-cells in such a specific or representative way that the
offspring will through its inheritance exhibit, even in a slight
degree, the modification which the parent acquired?_” (Italics in
original). The question is very precise and important, but I employ
that given above in preference as lending itself better to the line
of inquiry followed here.
I have placed this passage in italics because of its importance from
the point of view of the two problems which I am presenting and would
remark here that if only all the writers had used Professor Thomson’s
term “modifications” instead of “characters” in the statement of this
doctrine much confusion and evasion of plain facts would have been
avoided, and yet such workers as the Mendelians, if deprived of their
clear-cut term “characters” would have been less able to carry on their
studies. To this point of terminology I refer below.[30]
[30] The term “character” derives both from its etymological origin
and its application to biology a double-edged quality. This is of
great value to the study of Mendelism which can only or mainly
work with “unit-characters,” and it also serves the Weismann dogma
well. In both cases the term obliterates the conception of initial
variation, and while serving the purposes of these two great schools
of thought it directs attention away from the early minute and
unimportant stages by which many _germinal_ variations may have
arisen. If it had been coined for the purpose, which it was not, it
would have been a remarkable instance of polemic cunning. It will
be evident in the course of this study of initial variation, that
the accredited and general use of the term “character” begs the
question far too manifestly for the general use of biologists. If
it be retained for the neo-Darwinian and Mendelian provinces there
is nothing to say against it, but I adopt here with pleasure the
alternative term, often used by Professor Thomson, “modification.”
This is wide enough to include the more clear-cut “character” so
long as one makes it clear that the latter is one of the germinal
variations. Further, I hold that his use of the term “transmission”
instead of “inheritance” is the more useful for a wide range
of phenomena. As far as possible I shall employ the expression
“transmission of modifications,” instead of that well-worn but often
sophisticated expression “inheritance of acquired characters.” This
has been subjected by Sir Archdall Reid and Dr. Dixey, to say nothing
of others such as Mr. George Sandeman, to a somewhat bewildering
analysis. Thus the former says, “It follows that the so-called
“acquirements” are innate and “inherited” in precisely the same
manner as the so-called inborn characters.”* Dr. Dixey admits “that
all characters are both acquired and innate”** and goes on to say
that the accepted meaning of the terms was vague, that it led to
confusion, and that it ought to be dropped. For this remark of Dr.
Dixey one may be thankful, but of my friend Sir Archdall Reid I would
ask what he is doing in this galley?
* _Nature_, Vol. 77, Jan. 30th, 1908, p. 293.
** _Nature_, Vol. 77, Feb. 1908, p. 392.
Sir E. Ray Lankester in a letter in _Nature_, 21st March, 1912,
dissented from the mode of treatment of this point by Sir Archdall
Reid and presumably also by Dr. Dixey in the words “It is not, I
think, permissible to say that the normal characters which arise in
response to normal conditions are with equal fitness to be described
as ‘acquired.’” As to what is a normal character and what are normal
conditions there may be much reason for difference of opinion, but I
have said enough of this discussion to show that the terms “acquired”
and “character” would afford a biological Pascal some such food for
criticism as did the term “probable” in his _Provincial Letters_. The
less these two terms are employed the less misunderstanding there
will be of certain problems.
It has been held that “discussing words is often indescribably
tiresome, but it is better than misunderstanding them,” which is most
true.
In a world teeming with the life of plants and animals, and in the
branch of science which seeks to interpret them, where we enter
upon the unknown much sooner than in any other sphere of science,
Weismann has set out to prove or maintain the most stupendous negative
ever framed by the human mind. It would require generations of men
to _prove_ this negative, if it were probable, and his case rests
mainly on the assumed weakness of his opponents. So what is needed
and demanded from the neo-Lamarckians is the production of a few
well-attested and verified facts, and, as he admits himself, then it
must follow as the night the day that his followers will surrender
his characteristic dogma. The more cautious leaders and teachers of
the day say that this has not taken place and ask for facts, more
facts and still more facts, and this attitude is both judicious and
judicial, for example in a teacher so eminent as Professor J. Arthur
Thomson. Scientific men, in such a position as he occupies with grace
and distinction, owe a serious debt of loyalty to ultimate truth and
to the inquiring minds of the young students of to-day and to-morrow.
Those who are in a position of inferior responsibility and honour,
and more freedom, just rank and file members of the Commons’ House
of Parliament, may be pardoned if they do not exhibit an excess of
deference to authority and if they think for themselves.
Two Questions.
There are before the Scientific jury to-day two very vivid questions.
(1) Can modifications in the structure of an individual organism,
occurring as a result of its experience, be transmitted?
(2) What is the cause of variation?
If, as Weismann taught, the answer to No. 1 is in the negative, there
is little use here in trying to answer No. 2, for from the present
point of view the two stand or fall together in the study of Initiative
in Evolution. Such _distributional_ answers to No. 2 as Bateson and de
Vries may offer do not concern my purpose.
If No. 1 be answered in the affirmative it is sufficient for the
purpose of treating initial variations from the Lamarckian standpoint,
for it is hardly conceivable that Nature would neglect so simple and
obvious a method of leading upwards and onwards the organisms that
inhabit a changing world.
It is very clear from what is written on the subject of evolution
to-day that a _point d’appui_ in the process is earnestly desired
by many workers and that Weismann’s dogma stops the way. A very
significant and important remark is made by Professor W. McDougall
in his small book on Physiological Psychology, with reference to the
inheritance of acquired characters, that it is a “proposition which
most biologists at the present time are inclined to deny because they
cannot conceive how such transmission can be effected. Nevertheless the
rejection of this view leaves us with insuperable difficulties when we
attempt to account for the evolution of the nervous system, and there
are no established facts with which it is incompatible.”[31] I am aware
that in the scheme of observed nature there is evidence of no iron
necessity, that the convenience of psychologists should be provided
for, and they, like others of us, have to do the best they can with the
tools and the materials which exist, and I agree with Professor Thomson
in his remark on _Misunderstanding No. 1_, “that our first business
is to find out the facts of the case, careless whether it makes our
interpretation of the history of life more or less difficult,”[32]
but I am persuaded that he will not treat lightly _such_ a statement,
from _such_ a source, on _such_ a subject as that I have quoted from
Professor McDougall. As to his second statement on the same page
“that in the supply of terminal _variations_, whose transmissibility
is unquestioned, there is ample raw material for evolution” it is
important as an opinion, and no more, and there is in the present
connection, an elusiveness about it which prevents one allowing it to
pass. It should be noted that stress is laid upon the term “variations”
and from the context this means congenital full-blown “characters”
such as those that Weismann says are provided in the germ guided by
selection. At any rate, initial modifications are not signified by
Professor Thomson’s remark. So for _evolution_ of forms of life it is
possible the assertion may be true, but apart from distribution of
variations, under the process called amphimixis, some starting point is
required for the initial and wholly useless stages of many variations.
These may or may not become “characters” or adaptive.
[31] _Physiological Psychology_, 1911, p. 156.
[32] _Op. cit._, p. 179.
What the Problems are not.
The ground may be cleared here by saying what our problems are not.
There is no question as to whether Lamarckism or Darwinism represents
the predominant partner in the story of life; there is no question
of the “relative importance of natural selection and the Lamarckian
factors in organic evolution,” though such a question may arise when
once Lamarckism has received its passport from the authorities; but the
time is not yet. Nor is it a question as to the reason why adaptive
modifications are so constantly present in the germ. It is not a
question of Nature _or_ Nurture, but perhaps may be found to be a study
of Nature _and_ Nurture. It is not a question of Mendelian analysis,
nor as to the distribution of either mutations on the one hand, nor of
minute fluctuating variations on the other. The problems are therefore
limited in scope and ambition, and are none the worse for that, as
being better open to correction or support.
The Problems Considered.
It seems but natural to most persons who contemplate with any care the
ever-changing and progressive drama of life in plants and animals that
unquestionably the _dramatis personæ_ by their individual response to
the environments and exercise of their functions must contribute a
share, however small, to their offspring. When first this view presents
itself to their minds they resent as “unnatural” any other possibility.
But, alas! they find that such a conclusion is not permitted in those
regions where alone the white light of science shines. Here the writ of
_a priori_ does not run. The spirit of inquiry makes its challenge to
every presupposition and every assertion in its province--even those
of current science. I have shown that this particular assumption of
the natural man was firmly challenged by Weismann, who was not the
first, but the greatest, biologist to teach that modifications are
not transmitted. Accordingly, agreeable and convenient as it would be
to assume the Lamarckian hypothesis as a working one, it needs in the
present day to be supported by evidence before this can be allowed.
Facts, then, against Weismann’s dogma are demanded and of such a kind
as will satisfy so powerful an advocate of his own views. In passing
it may be remarked again that there is nothing so misleading as facts,
except statistics, and for both sides to bear in mind the warning of a
French writer that in such inquiries as this we should be careful lest
we find the facts for which we are looking.
To meet the conditions laid down in Professor Thomson’s Canon I
propose to describe certain phenomena which are adduced as instances
of modifications in certain mammals whose structure and mode of life
are intimately known, and whose ancestry is little in dispute.[33]
The most convincing of these lines of evidence are those which are
shown to be outside the range of any form of selection, as well as
the _distributional_ factors of Mendel and de Vries. It is well to
enumerate here the six different factors in organic evolution which
might claim a share in the production of such humble phenomena as form
the subject-matter of this volume--they are:
1. Personal Selection of Darwin.
2. Sexual Selection.
3. Histonal or Cellular Selection of Roux.
4. Germinal Selection.
5. Inheritance according to Mendelian principles.
6. Inheritance of Mutations.
[33] With the exception perhaps of the highest of all, for since the
publication of Prof. Woods Jones’ _Arboreal Man_ the question “Who is
Man?” has received a new answer.
There is a somewhat severe and ill-defined condition attached to the
formula in question for it demands that such modifications as will
satisfy the neo-Darwinians shall not be _correlated with any useful
character_.[34] If such a _conditio sine quâ non_ were taken too
literally it would at once foreclose the case as to the possibility of
transmission of modifications at all, the questions of issue ought in
that case never to have been raised--and, _cadit quæstio_. This cannot
be the intention of the biologist who propounds the formula. It could
not reasonably be carried so far as to insist that a modification
arising from a certain habit, active or passive, in an animal, and
which on that account, and on paper, may loosely be said to be
‘correlated’ with it, is to be ruled out. That would be tantamount to
saying for example, that, because an animal must lie down in a certain
attitude when it rests, or walk or run in a certain manner, in other
words that it is useful to exist, certain modifications claimed to be
due to these fundamental parts of existence must be excluded from the
inquiry. The neo-Darwinian is not a critic easy to be entreated, but
_that_ he would not claim. Let me take one example of what I mean. A
short-haired dog will spend a considerable part of its daily life,
and presumably a long line of ancestors did so too, lying with its
forelegs planted in front of its chest and its head either raised in
the air when awake or resting on the upper surface of the forelegs (of
course the familiar attitude of a dog with its body and head curled
up and fore-legs doubled is not referred to here). If the hairy coat
be examined over its neck and jaw, which lie in this attitude, on and
against the forelegs, a remarkable reversal of the direction of the
hairs is found and the outline of this forms an accurate mould of
the surface applied to the forelegs. This is transmitted of course
from previous generations of domestic dogs. A precisely analogous
reversal of the hairs is found on the under or extensor surfaces of
the forelegs, matching with wonderful exactness the area of pressure
of these on the ground, and anyone can see it who has a canine friend
of the fox-terrier type. Long-haired dogs display it less neatly
outlined. An instance such as this cannot be excluded from the evidence
forthcoming because it is correlated with the useful “character” of
lying in a certain attitude. Such a phenomenon, many similar to which
will be seen later, had at any rate an origin _de novo_ at _some time_
in the ancestral stock, and in _some way_. To discover these is part
of my business. The boldest neo-Darwinian will not claim that this
arrangement of a dog’s hair arose by selectional processes within the
germ either in the initial or completed stages.
[34] My italics.
Correlation.
The term “correlation” is somewhat scornfully said by Weismann to be
“unquestionably a fine word,” and it has indeed in biological writings
a very varied set of meanings. I will not vex the reader with a
reference to our old friend Mesopotamia, but mention what Dr. Vernon in
_Variation in Animals and Plants_ says of the term, referring to the
relation between stature and head-index in man: “Such a statement must
vary according to the notion of the observer as to what does and what
does not constitute correlation.”[35] The most approved and precise
meaning of the loose term in question is that associated with the work
of the biometricians, and a few examples from Dr. Vernon’s book will
show how far this conception of correlation is removed from the literal
application of Professor Thomson’s formula. Dr. Vernon treats of such
phenomena as the correlation of the long heads of greyhounds with
length of legs, contrasting them with the shortened heads and legs of
bull-dogs. He describes also the correlation in man between the stature
and length of forearm from elbow to tip of middle finger, correlated
measurements of crabs, of external structures of prawns, the tufts of
Polish fowls correlated with perforations in the skull, also certain
constitutional peculiarities with colour of skin. These few cases are
enough to give an idea of the more precise and fairer acceptation of
the term, but while these form a useful subject for minute study it may
be remarked that they agree also with Lamarckian factors as to their
origin and development. They are much more in line with Darwin’s use of
the word and are strangely reminiscent of the well-known example of the
Irish elk with its great head and horns which was brought forward in
favour of Lamarckism by Herbert Spencer. They breathe an atmosphere of
physiology rather than anatomy, or function than form.
[35] p. 74.
Enough has been said here by way of defining the terms of the issue.
The negative we have to sustain is that the following facts and
observations declare that certain small modifications cannot be
governed by selection and are not correlated with useful characters.
It will be shown later that Professor Thomson’s stringent condition
is not in all of them compiled with, but that, in spite of this, the
probability of their being valid examples of Lamarckism in practice is
immense.
CHAPTER IV.
INITIAL VARIATIONS AND TOTAL EXPERIENCE.
The present chapter is on _a priori_ lines and will perhaps be
dismissed with a wave of the hand or hurriedly skimmed over, but I pray
the reader at least to read the two or three last pages of it. It is
at any rate suggestive, and perhaps I may anticipate the comments of
the neo-Darwinian and throw myself on his mercy by mentioning a remark
of the late Sir Andrew Clark, prince of physicians and genial cynic,
which he made to a patient in my presence. A lady not distinguished for
depth of thought asked him a rather silly question in medicine. As if
offended he drew himself up, holding in his hand a cup of tea which he
was enjoying, and replied at once “Madam, you must get a younger and
more inexperienced man than I am to answer you that question.”
A very high degree of probability may be attached to the presupposition
that Lamarckian factors, even in their humblest form, may enter into
the story of the organisms as historical and living beings. Every
hypothesis in matters of science, or, to put it at its lowest, every
scientific guess must transcend the evidence at the time available.
Total Experience.
The suggestion I venture to make here is that if we take a
comprehensive view of certain two great groups of phenomena in nature,
which may be termed universal in their extent, it is difficult to
conceive that they are not causally connected in the sense that one
is the universal antecedent of the other. On the one hand are found
universal minute differences, not only between any pair of organisms,
but of any two corresponding parts of any organism, even to the size
and shape of each leaf on each plant. On the other is universal
discontinuity of _total experience_ of all organisms. This term
includes all the stimuli of use and environment to which an organism
is exposed throughout its whole existence, and its response to them.
It includes the whole succession of active and passive stimuli which
begin with the formation of a zygote in higher forms, for example, and
continue till the death or end of reproductive life of the individual.
It stands for such stimuli as arise from _habitat_ on or in the
earth, in various levels of salt or fresh water, in sea, lake, pool
and river, and in the branches of trees, from _climate_, from degrees
of _light_, _temperature_, _moisture_ and _wind_, from presence and
activity of _enemies_ and _rivals_, from _supplies of food_, from
_geographical_ and _topographical_ position. Such an enumeration of
stimuli might be much extended if it would serve any purpose. But it is
enough to say that the number of such stimuli, and the varying degrees
in which these are received and responded to, have hardly any limit
which we can conceive. It is a very different and harder task to find
out the proportion in which such stimuli are advantageous, injurious
or indifferent to the organisms, but it may be taken as certain that
the vast majority are indifferent in the sense of producing structural
change, and, that the advantageous stimuli transmit structural effects
to offspring, is only a matter of very strong probability. If the above
two groups of phenomena are not causally connected they are intertwined
with remarkable closeness and perversity. This aspect of the “web of
life” has received attention, and deserves more.
Discontinuous Environments.
Some reference must be made here to observations of Prof. Bateson in
his work on variation. In the first place he makes a most valuable
statement that “_the environment as the directing cause is essential
to Lamarck’s theory and as the limiting cause is essential to the
doctrine of Natural Selection_”[36] (which I venture to place in
italics on account of its importance to all who seek the pathway of
organic evolution) and points out also that “diversity of environment
is thus the measure of diversity of specific form. Here then we meet
the difficulty that diverse environments often shade into each other
insensibly and form a continuous series.”[37] This is clearly true
and important to the subjects he is discussing. But in regard to the
conception with which I am here concerned, that of _total experience_
of organisms, it must be remembered that there is no such thing as an
environment apart from the living beings that it environs, and that
from this point of view there is no such thing in the world of nature
as a continuous environment. The environment of two amœbæ living under
a cover-glass is, for them, far from continuous. In their infinitesimal
existence the exact position they occupy in the environing drop of
fluid, in which the proportion of their humble fare at one side of the
cover-glass is not the same as that on the opposite side, renders
their environments discontinuous, or different from that of another
amœba occupying a position and “environment” which _we_ should consider
identical. And this consideration applies to the other few “tropisms”
which enter into their little lives. This statement may be difficult
to prove, but it is a necessity of thought. An illustration may assist
one in visualizing such discontinuity. A fly is seen crawling at its
own pace up one of the great pillars of St. Paul’s Cathedral. It comes
to one of the thin layers of cement worn down with age and so delicate
that a man can just see it in a good light. The fly pauses, and passes
into what is for it a chasm, with as much relative deliberation as the
man would show in passing across a deep railway cutting. The number of
pictures that could be made of cases corresponding to that of the amœba
is incalculable. A few will suffice. Two plants of the common nettle
are growing on the south side of a ditch in a lane, one rooted a foot
higher than the other. The upper one receives throughout its life from
wind and sun stimuli slightly different from those received by the
lower, and from the soil slightly less moisture. These again receive
stimuli very different from another pair on the northern side of the
lane. Again in windy weather a clump of sycamores facing the south-west
in England, and situated on the ridge of an eminence, will receive
very different stimuli from a similar clump on the north-eastern slope
of this eminence, and will demonstrate the fact, as to force of wind,
by a marked slope to the North East. Even in either of the clumps the
individual trees present varying degrees of slope according to their
position. The total experience of these two clumps of sycamores and
of any two in each clump is obviously different. In a windy situation
you can tell in July which is the prevailing wind by noting the main
inclination of the ears of corn in a field. Again two male sticklebacks
in a pond will make nests for the eggs, there to be deposited, and one
will choose a spot on the southern and another on the northern side of
a little promontory of soil and stones at the edge of the pond. One
will find ready for him materials for building his nest different from
those of his rival, and he and his wife and family will receive for
that season very different stimuli, and so will the stimuli differ in
other phases of their existence in a pond occupying a few square yards.
On a sandy bank in a garden facing south you may discover two little
caves ingeniously hidden by a small opening, and in each of them you
can see a toad. Though these are only a few feet apart one is more
widely open to sun and wind than the other and one deeper than the
other, and whatever the other activities of the two toads may be in
their little shelters, they receive stimuli different in strength and
number. On another bank in the same garden less exposed to view, and
altogether more sheltered from sun and wind and enemies, a robin has
built a well-hidden nest. If the six fledglings in the nest are watched
when the mother is absent they are seen to occupy very different
positions of comfort, pressure and warmth. When the mother-bird returns
from marketing she is hardly impartial in the amount of food she
puts into their open beaks. But the slight and perhaps unimportant
inequality of their experiences as fledglings is nothing to that which
follows when they fly abroad, and which continues to the end of their
lives, the life of a robin being somewhere about ten years long. The
differences of the _total experience_ of the six young robins is easy
to picture. Again, surely, the total experience of two fleas on the
body of one plague-rat must be for such small creatures of importance
to their welfare, according as their respective “pitches” are on the
abdomen, back or legs of the host. When the life-history of a human
being is told in full the discontinuity of his total experience needs
no proof. The proof is written large before our eyes. But, perhaps, one
example may be given. There are two very eminent living writers, whose
light has certainly for some years not been hidden under a bushel, Mr.
Chesterton and Mr. George Bernard Shaw. We may be said to know them
well. Leaving out of sight the Celtic strain claimed by one, and indeed
all inherited differences, we see two men of perhaps equal ability,
near of an age, both living in London, both living by their pen, both
in easy circumstances. When one considers for a moment the different
company these two men keep, their different and opposing outlook on
life, their different and opposing forms of diet for their minds and
bodies (I know which of the two diets of those men I would choose and
with which of them I would prefer to be cast on a desert island) one
can only say that the total experience of Mr. Chesterton differs from
that of Mr. Shaw as cheese from chalk, which things, incidentally, are
an allegory in the philosophy of life.
[36] _Op. cit._ p. 6.
[37] p. 5.
The thought here briefly expressed falls well into line with Prof.
Bateson’s statement that the directing cause of the environment is
essential to the theory of Lamarck, and I do not hesitate to add to
it the assertion that _all environment_, in the wide sense of total
experience, _is discontinuous_. There are no such phenomena in total
experience as unit-characters of allied forms, small variations are the
rule. Without doubt a large proportion of the stimuli received by an
organism are as figures written on a slate and at once wiped off. They
are as the snows of yester year. The most they do is to contribute in
their measure to the metabolism of the organism, being too numerous
and minute to affect any structural change. In a higher form of life
none but those which are frequently repeated in the individual and in
succeeding generations can effect any structural response.
Mould and Sieve.
It will be remembered that a single example was given of a short-haired
dog in which its common habit of lying was associated with a certain
pattern of hair. This introduces and illustrates the very wide
conception of a moulding process undergone by an organism. It is one
familiar to biologists and very much so to Professor Thomson in his
various writings. Not less is he an exponent of the metaphorical work
of the sieve of natural selection. I therefore claim nothing new when,
with the temerity of certain persons treading where others are said
to fear to do so, I invent an inclusive term and propose to call the
two fundamental factors of organic evolution _Plasto-diēthēsis_[38]
in which the conceptions of mould and sieve are included and
hyphenated. This word is no more proposed for its elegance than are
_panmixia_, _amphimixis_ and _tetraplasty_, though perhaps it may be
the etymological superior of one or more of these. It is at any rate
inclusive and perhaps sufficiently audacious to assure the inventor of
the title of Dr. Pangloss of controversial memory. But as hard words
break no bones I have taken this risk and it would appear to be a
convenient “conceptual counter” and even Professor Karl Pearson could
not consistently forbid it. It has at any rate the merit of having a
meaning clear to all friends and opponents alike of Lamarckism. It
will be observed that the two words are placed in what I take to be
their natural order as expressive of the Alpha and Omega of the story
of organic evolution. The moulding process is claimed to precede that
of the sieve, as physiology precedes anatomy and function structure,
in that form of biological speculation which is held here to be the
soundest.[39]
[38] From the Greek. {Πλαστος from verb Πλαττειν to mould.
{διηθειν to strain through.
[39] The twin metaphor here chosen for the name of a complex natural
process should be cleared a little of a certain obscurity of meaning.
A mould is familiar to all in domestic and industrial matters, but
there are two sides to the metaphorical conception. A plastic object
may be moulded by the hand of man as in his ruder, but more laborious
days, or it may be pressed into an artificial mould that he has
made by means of his hands and tools. One of these we know in the
rude pottery made by prehistoric man and the vessel of the potter
described by Jeremiah the prophet. We know also those machine-made
moulds, so accurate as to be fitted for the coinage of a nation and
able to puzzle a clever coiner who tries to copy them. We know the
rough hewing of the stone by the sculptor which follows his moulding
of the clay. And in Sacred Writ we read of a double process when the
Hebrews not content with their object of worship took the golden
ear-rings of their women and Aaron “received them at their hand and
fashioned it with a graving tool, after he had made it a _molten
calf_.” But as no conception of a mould in biological matters, which
connotes the rigid accuracy of the coiner’s mould, can represent the
truth, the rougher and freer meaning of the term is here employed.
A similar double meaning is implicit in the metaphor of the sieve,
considered as a human utensil. I believe we owe this idea of a sieve
to Professor Thomson, but am not sure on this point. But I have not
been able to find any definition as to the way in which the sieve of
natural selection is held to act. A sieve is of course for sifting
substances, and the size of the mesh is adapted by us for the purpose
we have in view. We may want a sieve to hold back for us the fit or
good and allow the unfit or bad to pass through, for example wheat
and chaff, or we may employ it to separate sand for our purposes from
fine gravel. The former is of course the most common of the purposes
for which a sieve is used. So here the comparison of personal
selection with the action of a sieve agrees with this aspect of a
sieve, the fit being retained and the unfit allowed to pass through,
thus agreeing with that view of Spencer’s of the survival of the
fittest which is held by most authorities to be more accurate than
Darwin’s Natural Selection.
So the banns between Lamarck and Darwin are published, not for the
first time of asking, and who shall say that there is cause or just
impediment why these two should not be joined together in holy
matrimony?
I conclude this chapter with a passage from the life of Columbus by
Washington Irving which affords a fitting parallel from history in the
higher development and union of two formerly hostile Kingdoms, and the
moral of it is clear and simple. But as a forensic junior I beg to
enter a _caveat_ to the effect that though the name of Columbus occurs
no suggestion is made of the discovery of a New World.
“It has been well observed of Ferdinand and Isabella that they lived
together not like man and wife whose estates are in common, under the
orders of the husband, but like two monarchs strictly allied. They had
separate claims to sovereignty in virtue of their separate Kingdoms,
and held separate councils. Yet they were so happily united by common
views, common interests, and a great deference for each other, that
this double administration never prevented a unity of purpose and
action. All acts of sovereignty were executed in both their names; all
public writings subscribed with both their signatures; their likenesses
were stamped together on the public coin, and the royal seal displayed
the united arms of Castile and Aragon.”
CHAPTER V.
METHOD OF PROOF.
In a matter of scientific inquiry one cannot go far wrong if one
follows the advice of Henri Poincaré, who lays down certain principles
of method; four of these are the following:--
(1) The most interesting facts are those which can be used several
times, those which have a chance of recurring.
(2) The facts which have a chance of recurring are simple facts.
(3) Method is the selection of facts, and accordingly our first care
must be to devise a method.
(4) We should look for the cases in which the rule established stands
the best chance of being found fault with.
The groups of facts described in the succeeding chapters are in
agreement with these principles in the main, and are perhaps like a
dust heap for their intrinsic value. But one knows that before now
among a good deal of _débris_ a rusty key has been found which has
opened a cabinet containing certain treasures, and in the hands of
someone else than the finder has produced useful results.
The headings of the chapters describe the facts, and there is no
need to enumerate them here. The first and largest group is studied
according to a method which is in a measure applied to all the others.
Most of them are external or superficial phenomena and accordingly are
open to others beside the expert for observation and corroboration, or
the reverse. The typical plan adopted is as follows: a large number
of related phenomena are chosen, and the more prominent of these are
observed and described. Keeping in mind the two plain issues laid down,
the origin of initial modifications and their transmission, I have
selected the facts because, especially such as those of the hair, they
are very simple, of wide distribution in animals well known to us,
such as the domestic horse and man, and none are brought forward which
any other observer cannot study for himself if he has some anatomical
and physiological knowledge, some training and care in recording
observations. In most centres of population there are still left a good
supply of horses in streets and stables, of preserved specimens in
museums and living ones in zoological gardens, and of hairy young men
who will hardly refuse a polite request to examine the minute hairs
clothing their trunks and limbs. One has to pursue a certain amount
of that study which may be called the sister of plant-ecology, that
is, animal-ecology or the behaviour of animals at home. The student of
these matters, it may be freely admitted, will complain, unless he has
some hypothesis or line of thought to follow, that he has been set down
in a valley in which the bones are very many and very dry. But, armed
or primed with an hypothesis, he may find an affirmative answer to his
question “Can these bones live?” Every group of natural phenomena,
_without exception_, has some meaning for those who will interpret
nature rather than bully and slight her, and whatever anointed king
may claim sovereignty over it the humble fact cannot be denied that
“whatever phenomenon is, _is_.”[40] Again I would refer to Howes’
inspiring note: “We live by ideas; we advance by a knowledge of the
facts; content to discover the meaning of phenomena, since the nature
of things will be for ever beyond our grasp.”[41] The facts adduced
are simple, have a chance of recurring and are widely distributed
among multicellular animals--the botanists and plants can very well
take care of themselves. I must once more state that I am attaching
to the considered facts a value of a somewhat unusual kind--_their
intrinsic unimportance_. For anyone who has had to encounter the
skilful dialectics and counter-attacks of a well-equipped neo-Darwinian
it is well that he should remember the maxim of Napoleon, “Be
vulnerable nowhere.” It is necessary to show evidence for Lamarckian
factors in which no degree of selective value, survival-value, can
be seen by hostile sharp-shooter while he works in his trench. The
main line of defence, or more correctly what Hindenburg would call
“offensive-defence,” is therefore made to rest on the phenomena of
hair-direction, which, I submit, are impregnable to the forces of
selection, probably in all the hairy mammals, but certainly in that
hairy animal called Man.
[40] Jevons.
[41] British Association of Science 1902. Zoological Section.
Thesis.
If these groups of phenomena were being studied apart from the
hypothesis they support, a much more full treatment of all of them
would be required, such as I have given to those of hair-direction in
a book published in 1903 on _Direction of Hair in Animals and Man_.
The limited thesis, however, here upheld is that the phenomena are
produced by the factors of stimuli and response in the course of
the total experience of the organism, that the essence of the matter
is the production of initial modifications, that instances of these
in well-known animals are produced before our eyes by ascertainable
mechanical stimuli, and that, especially in those of hair-direction,
experiment is adduced in proof of the thesis that some modifications
are transmitted.
Procedure.
The order of proceedings may be tabulated thus:--
(1) Observation of selected facts.
(2) Evidence that certain of these are produced in the lifetime of
the individual.
(3) Evidence that among the facts of direction of hair and others
there is to be seen an orderly evolution rather than a casual
appearance of the changes noted.
(4) An hypothesis as to their production.
(5) Exclusion of selection as a possible cause of these, and of
correlation as properly understood.
(6) Experiment in verification of the Lamarckian interpretation of
the phenomena.
And here, before I hear some Prince Henry of the genus Weismann, Mendel
or Gallio groan aloud: “This intolerable amount of sack,” I proceed to
offer him a few loaves of home-made bread.
CHAPTER VI.
EVIDENCE FROM ARRANGEMENT OF HAIR.
_Ex Uno Disce Omnes._
The singular arrangement of hair on the forearm of man is the subject
of some curious statements by Darwin, Wallace and Romanes, and these
suggested to me twenty years ago the following line of thought. To many
minds the text will appear a humble one, but it opens many avenues of
inquiry.
These three illustrious men are all more or less inaccurate and
incomplete in their descriptions of the hair on man’s forearm, though
Romanes[42] gives a drawing which supplements his written account.
They looked upon it as a vestige of the pattern of hair on the forearm
of existing anthropoid apes, especially the orang, in whom its
fully-developed form was an adaptation governed by Natural Selection.
Of the three, Wallace is the most uncompromising on behalf of this
view, Romanes rather accepts it _en passant_, and Darwin in a long
passage[43] adopts it with some reserve and his usual respect for the
work of his great co-worker, as the most probable explanation of a fact
which lay heavy on his scientific conscience. Indeed, for all these
great men it was a _crux_, though Romanes, with his Lamarckian views,
need not have found much difficulty with an alternative account of
it.[44]
[42] _Darwin and after Darwin_, Vol. 1, p. 90.
[43] _The Descent of Man_, Chap. VI., p, 151.
[44] I may remark that Darwin seems at an earlier date to have made a
very curious suggestion in this connection, for Hartmann, in his work
on Anthropoid Apes, p. 99, quotes him as saying: “We should, however,
bear in mind that the attitude of an animal may perhaps be in part
determined by the direction of the hair; and not the direction of the
hair by the attitude,” a notion so obviously untenable that it does
not appear in the second edition of _The Descent of Man_, 1896.
At the time when these statements were made, the lineal ancestors of
man were much more definite personages than they are now, as Arthur,
the legendary Celtic hero, was formerly held to be an historical
personage more than is the case now. These ancestors were generally
believed then to be found among the four existing anthropoid apes.
The picture of our ancestor among the apes, as given by Wallace, in
connection with this state of the hair on his forearm, represents
him as spending much of his time like the gorilla, who, according to
Livingstone, “sits in pelting rain with his hands over his head.” He
would no doubt find the thatch-like arrangement of the hair a tolerably
efficient umbrella, but one may doubt very much if so clever a denizen
of the tropics would fail to find under the great branches of trees, in
a tropical forest, a better covering and one more like the roofs of our
houses. But when we cannot find a roof to our heads we--and the orang
or gorilla--naturally employ a substitute, and not otherwise. Be that
as it may, it is doubtful if the thatch of his forearms would supply
him with that survival value on which the theory of Selection depends,
to say nothing of the fact that in its incipient stage the reversal of
the slope of hair, inherited from the lemur stock, would be trivial and
useless.
But one must ask: “Did man’s Simian ancestor really loaf away so much
of his time in this dull manner? and was the running-off of rain so
frequent and imperative a need as to make him set to work to invent
this special adaptation?”
After some millions of years have passed since his day we are not in a
position to go beyond speculations, and this one seems barely credible,
moreover, it is quite unnecessary, as certain following facts will show.
Steps of the Inquiry.
Having expounded the text and its context, I would mention that in
1897 I came across these views of biologists as to the very strange
arrangement of hair on man’s forearm, and was struck with the
inadequacy of the theory of Darwin, Wallace and Romanes to account for
the state of things which every man can find, if he looks for it, on
his own forearm. I examined a large number of apes and monkeys so as to
test the theory, and the results were published in _Nature_, Vol. 55,
under the title “Certain vestigial characters in Man.” Suffice it to
say that from the evidence I brought forward one had to choose between
two heresies: either to deny the Simian ancestry of man or to affirm
the inheritance of some acquired characters; and I chose the latter.
The choice of “evils” or heresies which had to be made then will serve
as an introduction to all that follows.
This article was followed by a paper at the Zoological Society of
London on “The Hair-Slope in certain Typical Mammals,” and after this
came a paper at the same Society, giving evidence and reason why
certain patterns of hair in some mammals should rank as specific
characters. Various other papers at the Anatomical Society of Great
Britain and Ireland were read and published and others at the
Zoological Society, in which different regions of the hairy coat of
man and lower mammals were dealt with. In 1903 the whole subject of
the Direction of Hair in Animals and Man was treated in a book freely
illustrated.
I then followed the advice of Horace and left the subject alone for
nine years, during which time my further observations and reflections
served but to confirm, except in two or three unimportant details, the
results and conclusions in the book and papers of an earlier date.
The connection between the habits of an animal and the distribution
of its hairy coat were always cropping up, and I saw then and see now
no possible explanation of the connection than that the former is the
efficient cause of the latter.
How the Hair is Arranged on the Forearm.
Returning now to the text, the remarkable arrangement of hair on man’s
forearm, attention may be directed to the accompanying figure of the
forearm of a lemur, an ape and man, in which the extensor or back view
of this limb-segment is shown, the heavy “war-arrows” being employed
to direct the attention of the reader to the main lines in which the
hair-streams flow. The front or flexor surfaces in the lemur and
ape are not shown because they are precisely like the corresponding
back surfaces, and the flexor surface in man is shown in the figure.
The figures are so much like diagrams that a very little detailed
description will suffice. For the examination of the hair on man’s
forearm the best subject is a dark-haired youth, and it is easily
traced, though in any hairy subject it can be shown up well by placing
the forearm in water for a minute and allowing the water to drain
off. The normal and congenital hair-slope on the forearm is then well
displayed.
On the front surface of man’s forearm the hairs point away from the
elbow and divide in the middle of the surface into two streams, one
passing to the outer and the other to the inner border in a downward
gentle curve, and they join the streams of hair on the back surface. In
this pattern there is nothing very peculiar, for it is shared by many
monkeys.
When the back surface is examined it is found to present an arrangement
of the hair which is _unique_ among hairy mammals. The figure shows the
eccentric course taken by the hair on the back surface. In the centre,
exactly along the extensor border of the ulna, from the wrist to the
point of the elbow, the hair-stream has been bold enough to turn
straight _upwards_ in a narrow line, and it was here that our three
great leaders saw their chance of claiming for Selection a tiny bit
of territory, a kind of Duchy of Luxembourg between two great States,
though, as I proceed to show, the claim is disallowed and untenable.
[Illustration: Fig 1.--Arrangement of Hair on the Forearm.]
In the ape the hairs of the forearm are much longer and thicker than
those of man, and both on the front and back all point _from the wrist
to the elbow_.
In the lemur all the hairs point _from the elbow to the wrist_.
In the products of Nature there are no freaks, or impish tricks
performed, and it is not for nothing she does her work. Every one of
them asks for and should receive an explanation consistent with fact
and reason, and here comes in the need for studying, as one may, the
broad outlines of man’s ancestry. His ancestor being now sought in an
earlier and more generalized stock than that of the four genera of
anthropoid apes known to us, the most instructive and safest line to
take is to trace him back to the stock lemur, who remains to-day among
the most Chinese or unchanging of known mammals. In his illuminating
work, _Prehistoric Man and History_, Professor Scott Elliott adopts an
excellent term, “lemur-monkey-man,” to sum up, without missing links,
the long ancestry of man. I take the liberty of adapting this term more
closely to the present inquiry and use that of _lemur-ape-man_ instead,
for whatever may be the relation of man to present apes some ape-like
ancestors enter into his genealogical tree.[45] For my purpose the
monkey is less useful because his hair-slope differs so little from
that of lemurs, whereas apes have made for themselves a very remarkable
position as regards the hair of their forearms. Our series of animals
for study is then well represented by the lemur-ape-man--hypothetical,
necessary and serviceable. Through all the immense stretch of time
occupied in this process of descent there has been ample opportunity
for the lemur to change his fashion to that of the ape, and the latter
to change to the present fashion of man.
[45] This was written before the publication of Professor
Woods-Jones’ book _Arboreal Man_.
This simple arrangement of the lemur’s hair is common to that of all
the more primitive long-bodied mammals, of which an otter is a good
example, and I venture, greatly daring, to call this the normal slope
of hair. Somewhere and somehow in the human tree there has appeared
a total reversal of the lemur-type; the stock of apes acquired a new
fashion, and gradually discarded altogether their ancient inheritance,
beginning their innovation perhaps, with _Dryopithecus fontani_ in the
Miocene Age.
The Dynamics of Hair-Pattern.
There are a few well-known facts which it is necessary to bear in mind
if one is endeavouring to understand the mode of origin and order
of the events before us. The hairy coat of a mammal is composed of
individual hairs of varying length, colour and thickness, each being
rooted in a tiny pit in the skin and growing from a papilla at its
base. As the hair grows, its free end is pushed away from the papilla
at the rate of one inch in two months. This is the rate in man’s hair,
and it is probably greater in the case of lower mammals on account
of the greater importance and physiological activity of their hairy
coat than in man’s. But one inch in two months is a close enough
calculation. Here, then, is a structure which grows throughout the
whole life of the animal, and has to dispose itself somehow on the
surface of the skin. It does this _in the line of least resistance_,
and to trace this line is the Alpha and Omega of the present inquiry.
There is a conception of much value in understanding the dynamics of
the distribution of hair, and that is to view the hair of mammals as
composed of certain streams. As in every illustration, this conception
may be challenged because of some difference the critic may find
between these streams and a stream of fluid. It certainly does not
leave its bed as do the component parts of a river, a glacier or molten
lava, for the base of the hair is fixed. But it will serve, and is
at least not more open to objection than certain useful metaphors in
biology as when the genealogy of man and animals is pictured as a tree,
or the living things of the earth as a “web of life.” It is, then, as
_streams moving at the rate of one inch in two months in the lines of
least resistance_ that I propose to discuss the animal hair and its
diverse patterns and offer no further apology for doing so. Just as
in the cases of a stream of water with varying banks and rocks in its
course, or a glacier with its mountain-sides and sinuous valleys, or a
stream of lava with small projecting surfaces of a mountain, our stream
of hair flows on, hindered only by adequate obstructions.
Yet another conception from the region of metaphor must be mentioned.
It is one which will commend itself to every mind which has been
steeped in thoughts of warfare for five years. We are all soldiers now;
we think in terms of military affairs. In the case of our hair-streams
there are in many regions two forces directly opposed to one another,
others in which no struggle has yet occurred, as, in the Great War,
Italy was not at one period at open war with Germany.
Between the opposing forces in our small battle-field of the hairy
coat there have been waged battles to which those of Mukden, Verdun,
the Somme and Arras, are not to be compared in point of time. They
are but as one day to a thousand years. On one side of the conflict
in our present chosen field the ancient primitive type of the lemur
has remained entrenched for some millions of years, until there arose
new forces in its descendants on the other side and this changed the
war of positions into one of movement. It was indeed “a contemptible
little army” which came forward to oppose the ancient barbarian
forces of the lemur, long prepared and organised, and these new
armies fought under the banner, Habit. In the slowly-formed patterns
in many types of mammals we have records of the treaties made after
these long struggles and the rectifications of frontier which became
necessary. The critic may call these “battles of kites and crows,”
and ask What war correspondents were allowed to describe them; but a
battle, whether great or small, long or short, is important to the
parties concerned, and it is open to us to “reconstruct” the facts of
the battle as do the historians on their part, for example, Sir James
Ramsay the battle of Agincourt--with tolerable verisimilitude. But in
science, especially geological science, the process of reconstruction
is much more ambitious and bold than any that is here attempted. Who
has not been fascinated, if he has read Sir E. Ray Lankester’s work
on Extinct Animals, by the skill and daring with which he conveys to
us a vivid idea of the form and mode of life, with scanty data, of
the extinct Moa of New Zealand, the great Pterodactyle, Pteranodon,
or the Diprotodon of Owen--“the probable appearance in life” of these
uncanny but very real inhabitants of the earth in days long past. How
skilfully did Owen from a piece of bone seven inches long, sent to
him by a gentleman in New Zealand sixty years ago, pronounce it to be
a part of the thigh-bone of a bird like an ostrich, and then after a
few years had passed, confirmed it by more bones of the skeleton, till
the large Moa, extinguished 600 or 700 years ago by the Maoris, lived
again before us--an historical personage; or how by the examination of
the skull and most of its skeleton the giant marsupial from Australia,
Diprotodon, was resuscitated and admired; or again, how from the bones
of the arms, shoulder-girdle and fingers was built up the strange body
of Pteranodon, the great flying dragon. All of which is the legitimate
and approved business of biologists and palæontologists, and this
digression is made here to show that my line of treatment of a little
subject agrees with that in a greater one; nay, it even proceeds in
its explanations of events on the ever valuable principle of Lyell in
a still greater one without which to-day geology would be a thing of
naught, that is, the principle of _explaining changes in the surface of
the earth by reference to causes now in action_. The objection that one
subject is very great and the other very small is not valid; for one as
much as the other there are millions of years to be had for the asking.
Who in these days hesitates to talk and try to think in millions?--tens
of millions of men, millions of soldiers, millions upon millions of
money, millions of bacteria in vaccines and millions of money belonging
to other people disposed of by the new spendthrift Minister?
From Lemur to Ape.
Returning now to our Eocene lemur we must remind ourselves of the
problem before his simple mind and those of his Simian descendants. How
was he to change so greatly the direction of the hair on his forearm
(Fig. 1) till it should turn right about face and imitate those great
German “victories” of Hindenburg, well called Marshal Rückwarts? The
problem lies open in the Figure and receiving no aid from Selection or
survival of the fittest, in this little effort, he had to fall back on
the eternal and tedious force of habit and use. I am afraid if here I
were interrupted by some critic, more learned than wise, by a summary
demand on the part of Selection for its share in the result, I should
be tempted to reply with the word Φλυαρια employed by George Borrow,
forbearing to give the translation of the reply as he gives it. Anyhow,
it is a case in which to “listen politely and change the subject.”
Here comes in the aspect of strife between primitive and new
obstructing forces in a little hair-stream. The lemur lives in trees
and carries on a stealthy nocturnal business, moving on all fours in
quest of his daily bread, and no external force or new habit avails to
modify the hair-slope on his forearms, and so it remains until some
primitive form of monkey, gradually evolving into a primitive ape,
brings into the family new habits and customs. Other men and other
manners appear in the Miocene Age. Our supposed Dryopithecus fontani
becomes more upright in his bodily, and perhaps his moral habits,
and spends an increasing amount of his leisure time in the sitting
posture; his hands are frequently grasping a bough as he sits and
reflects, it may be in a man-ward direction, or, as is more likely, on
his last meal of nuts and fruits. But he did not spend quite so much
time as Wallace and others think in this futile attitude, for he knew
in his way as much as the modern bachelor does, of making his posture
comfortable and restful when he was not out at work, and he varied
his plans by resting his forearms on his thigh, crouched up and cosy,
and doubtless slept much in this attitude. All these bold departures
from his lemur-ancestor’s habits had the necessary result of altering
the slope of his hair on the forearms, which was now growing as long
and coarse as we see it to-day in the orang. In course of milleniums
the ancient forces yielded to those of the new armies, and the once
normal slope became reversed in a way which shocked the conservative
lemurs of his day. It requires little imagination to see how the
lengthening thickening hairs on this limb-segment became changed in
their direction by friction against the opposing surfaces of the
thighs, by gravitation, and the frequent dripping of rain when they
were held up to grasp a bough. Here then we see at work new forces of
friction, pressure, gravitation and dripping of rain, turning endlessly
and slowly the lemur-fashion into the ape-fashion, with unlimited time
for their effectual action. In this stock of Man’s ancestry Selection
was taking care of the individual and Habit of the details of his
making--two truly harmonious partners.
From Ape to Man.
Another step, and a long one, has still to be taken from the
ape-fashion to that of man. Bearing in mind that the lemur-fashion has
been totally reversed by the ape it startles one to find that man in
his modern fashion has largely reverted to that of the lemur on the
front and sides of his forearm. This is clearly shown in Figure 1.
There also you see graphically recorded in the hair of the extensor
border of the ulna, a little _backward_ streak, a poor little legacy of
fifty pounds from the fortunes of many thousands once possessed by the
ape. From the present limited point of view, man is a veritable pauper,
and his possessions in this limb-segment may with some irony well be
called a “vestige.”
Professor Scott-Elliott in his book, _Prehistoric Man and His Story_,
p. 60, goes rather wide of the mark here in his graphic picture of our
rude ancestor and his hard life. He gives too strongly the idea of
him sitting asleep in raging gales, in driving rain which is neatly
conducted by the thatch of his hair off his skin. As far as it goes
this need not be questioned, as a matter of probability, but he states
far too broadly “The hair on the arm, even of those civilised men who
retain sufficient to trace the arrangement, turns down both upper
and forearm to the elbow”[46]--true as to the upper arm, but only
true of the forearm in a very narrow streak of hair over the extensor
surface of the ulna. The fact is that in every human being, not too
old, its course can be traced with a lens. He overlooks also from
this protective point of view the fact that the ape or early man, in
the position of rest he describes, would have very much the reverse
of protection from the “lie” of the hair on his thighs, for this is
towards the knee and is well calculated to catch the rain and conduct
it carefully, or let it run, into his groins. So the protection theory
(under the empire of Selection) is again in straits. But I must not
forget my self-denying ordinance alluded to in the Preface, but will
show how the ape fashion began to be modified into its present and
probably final form in man. Still further changes in the simple habits
of the earliest men became frequent, and fresh forces were organised in
our mimic battlefield. Gravitation gradually ceased to act as the hairs
became thinner and shorter. Friction and pressure changed their lines
of incidence with the increasing tendency of man to assume the upright
posture, for the surfaces exposed to pressure and friction were only
affected when the extensor surface or back of the forearm rested on
some supporting object, an attitude extremely common in man as we know
him now. Then came the opportunity of the primitive barbarian host, the
lemur fashion, by a prolonged counter-attack to recover on the greater
part of the forearm the ground lost millions of years before by the
ape, and then was engraved on the forearm of man the permanent treaty
which we have before us to-day.
[46] _Prehistoric Man and His Story_, p. 60
This small and apparently trivial battle-ground has been described at
what may seem undue length, but it is a miniature of the rise and fall
of little empires such as here engage our attention, and I make no
apology for this to the reader who has gone thus far with me, for, on
the principle of _ex uno disce omnes_, all that follows in other areas
of the hairy coat of mammals will be the clearer, and little repetition
will be needed.
NOTE.--Two terms have been used somewhat freely in this Introduction,
“vestige” and “normal,” and a few remarks upon them are not out of
place, for they are both somewhat ambiguous and apt to be carelessly
employed.
A vestige in biological writings is almost the exclusive property
of the Pan-Selectionists, and no one can doubt that on the one
hand it is a far more correct term than that of rudiment which
Darwin employed so freely, on the other that they have a perfectly
legitimate claim to it in a large number of obsolete structures of
animal forms. But vestiges, footsteps, footprints, have another and
equally correct meaning, even if less often thus employed, in the
fact that a vestige or footprint may just as well be a relic of
what the race and individuals have _done_, as a relic of what they
have _retained_ in the way of possession, and I submit that the
facts and arguments I have here advanced afford a valid claim to the
term “vestige” in the results of certain _doings_ on the part of
animals--as will appear later still more clearly.
The term “normal” is a fine field for dialectics, but neither
ordinary men nor scientific students can do their work without
its use, and yet it would have been an intellectual treat to
have heard how Huxley, for example, would have turned inside out
any opponent who chose to employ it to his dissatisfaction. In a
strictly-conducted tournament no evolutionary biologist would allow
its use--to his adversary. A norm for him exists only as one of
Professor Karl Pearson’s “conceptual counters,” a piece of mental
shorthand or hardly more than a _pis aller_. Among the fundamental
conceptions of organic evolution there is one which is almost a
truism, the doctrine of Heraclitus, πἁντα ρε̑ι, the everlasting flux
and change of Nature and her products. In strict logic, according
to what we all now believe, there is no possible norm. All that one
may do is to take stock at a certain epoch of evolution and label,
for our own convenience, some group, or organism or structure as
“normal”--and go on with our business, collecting some specimens,
calling them type-specimens, and putting them in books or cases in
the Natural History Museum--and then proceed to business.
The biological teacher in his class room says he must live, he must
have his tools for his work, to which the idle student replies under
his breath, “I do not see the necessity,” but then few students
are now idle, and this jibe does not sting any one! The examiner
must have his normal human anatomy, and would ruthlessly plough
any daring examinee who tried to sophisticate the meaning of the
term “normal.” I have often been struck with what I must call the
intellectual audacity of a most eminent leader in physical science
and mathematics, who is not unlike a certain great Church, which
grants nothing to her adversaries but is not averse from taking. In
his _Grammar of Science_, written with a pen dipped in hydrochloric
acid, Professor Karl Pearson four times over, and perhaps more,
has the courage to call the human brain in this twentieth century
“normal.” Has he never heard of the coming Superman of Mr. Bernard
Shaw and other prophets? Thinking _sub specie aeternitatis_ has he
here in the West, and at a certain small epoch of time, any right
to call the human brain “normal”? I can only long that there may be
more normal brains such as Professor Karl Pearson’s, and am almost
inclined to echo the prayer of Moses, “Would God all the Lord’s
people were [such] prophets”! These comments on the term “normal”
imply no complaint against its use, indeed are a claim for it, and I
deprecate very much that form of criticism known in boys’ schools,
domestic circles, and among politicians as the _tu quoque_ reply,
and I hope the few ambiguous terms used in this book will pass the
censor, and help the reader.
CHAPTER VII.
THE EVOLUTION OF PATTERNS OF HAIR.
Some attention must here be given to the supposed mode of formation of
individual patterns of hair, that is to say, their evolution. So here
one has to move among the fields of hypothesis, without which detached
facts of nature are useless to science.
The simplest pattern consists of a reversed area of hair appearing
between two adjoining streams; the more complex are whorls, featherings
and crests. No detailed description nor illustration of the former
are required, but I have prepared a diagram to illustrate the latter
(see p. 51.) (A) shows a whorl by itself; (B) a whorl, feathering and
crest. The arrows at the sides indicate the direction of the adjoining
hair-streams, the arrow in the centre of (B) the direction of the
reversed flow of hair.
An understanding of the dynamics of a hair-whorl leads quite simply
to that of a feathering and crest, for the two latter are only the
results of the further extension of the battle of forces concerned
in the whorl itself, and the end of their conflict. A whorl marks a
point in the stream of hair where two contending forces have come
into collision; on the one hand the centrifugal force of growth from
each hair-papilla, the rate of which has been described, and on the
other a certain centripetal dynamic force which may be either that
of localised _friction_, _pressure_, _gravitation_, or _muscular
traction_, directly opposing or divergent. Thus conceived a whorl may
be looked at symbolically as a written treaty between two nations,
one of which has defeated the other, and actually as a proof that the
contending centrifugal and centripetal forces are in the state called
the balance of power. But when the centripetal force of some habitual
action prevails over that of the original force of growth in the
hair, a whorl becomes extended into a feathering, and the length of
this, metaphorically speaking, corresponds with the duration of open
fighting, and terminated by a sharp crest when another and a decisive
battle has been fought. A crest may again be looked upon as a “treaty.”
The whole process pictured here shows a battle followed by a treaty or
truce (W) again a retreat (F) and a counter-attack (C) with a final
treaty and peace.
This hypothetical treatment, with addition of some metaphors, does not
carry us far enough to leave it thus to the tender mercy of that class
of critic who relies too much on the “argument from ignorance.” He
tells us such a process as I have pictured may be true or not, and that
no one can do more than leave the case open, and treat it like that of
Jarndyce & Jarndyce where it would remain in Chancery till all of us
concerned in the inquiry have returned to our dust. The critic might
reasonably ask for experiments which will bear out the suggested views.
But verification by calculated experiments is impossible, for, _ex
hypothesi_, the variations or patterns which are described require long
periods of time for their production. Such experiments being ruled out,
the evidence in favour of the hypothesis must be sought in some region
of the hairy coat of mammals where whorls, featherings and crests can
be observed in all stages of their formation.
[Illustration: Fig. 2.--A. Diagram of a whorl. B. Diagram of a whorl (W)
a feathering (F) a crest (C).]
The Side of the Horse’s Neck.
The field chosen for observation is, from one point of view, the most
remarkable among all the numerous regions in the great series of
hair-clad mammals. The side of the neck in the domestic horse displays
all degrees and forms of whorls, featherings and crests in such variety
as to be almost bewildering. I must have examined many thousands of
specimens of this valuable large mammal in reference to this state
of things on the side of its neck, and can only regret that I have
not kept any record of them as to number or quality, and I fear the
opportunity for doing so will not return in this country. There are
three reasons for this choice of field. In the _first_ place there is
or was an extensive supply of the specimens for examination; in the
_second_, the side of a horse’s neck is a region where no extraneous
or artificial agents, such as harness, except a bridle, can operate,
and therefore Nature and the animal’s habits have free play; in the
_third_ the neck of a horse in its locomotive life is subject to
powerful mechanical forces which are _constant_, literally speaking,
while it walks, trots, canters or gallops. Here then, if anywhere, one
may read the records, in indelible characters of hair patterns, the
history of its active life and that of its ancestors, and here also one
may reasonably expect to find these patterns in every possible stage
of formation, from a mere rudiment to the most finished product in a
whorl, feathering and crest--_and this is precisely what is found to
exist_.
Even an observer not acquainted with the anatomy of this region who
watches closely a horse in action cannot fail to notice how at every
step taken there is a marked jolt of the neck produced in the neck by
the impact of its hoofs with the ground and in supporting its heavy
skull. I have computed several times the number of jolts that the neck
of a trotting horse sustains, in my numerous rides behind various
horses, during many hundreds of miles, and have reckoned the number
which occur in a horse trotting for an hour, at the usual rate at which
a doctor travels. This is on the average 6,000, and of course the
numbers of jolts in walking, cantering, and galloping vary according to
these different paces. But a great deal more of movement of the head
and neck is observed beside the jolt at every step. See how the animal
tosses up its head, twists it to this and that side for the mere _joie
de vivre_ when it is fresh, or, even when hindered by blinkers,[47] how
he turns his head to look at every passing object in the road with his
ancestral caution, how he will pass contemptuously a great horse-waggon
or even now a villainous-looking motor lorry, but will peer at a beggar
woman sitting beside the road, or a heap of stones, or a yapping cur!
All this vivid muscular work of a horse’s head and neck hardly ceases
while he is in action and at any rate not till he is dead beat, and
the higher the courage and breeding of the horse the more frequent and
brisk are his movements. Is it possible to conceive a region of the
body of any large mammal where more numerous, varied, and powerful
action of underlying muscles can be found playing their ceaseless
tricks on the sober normal slope of hair in the skin which covers them?
If there be any region approaching this I have not found it.
[47] Blinkers ought long ago to have gone the way of bearing-reins
for draught horses. If a riding horse does not need them, no more
need a draught horse be thus insulted, for very little intelligence
and patience on the part of their drivers would have educated their
excellent brains into indifference towards startling objects.
[Illustration: Fig. 3.--Superficial muscles concerned in the movements
of the head and neck of the horse.]
[Illustration: Fig. 4.--Deeper layer of the muscles concerned in the
movements of the head and neck of the horse; the scapula removed.]
The main facts of the anatomy of the horse’s neck must be referred
to here, so that a better picture may be obtained as to the powerful
forces which are found in conflict during the locomotive life of the
animal. Fig. 3 shows the superficial layer of muscles concerned in
the actions of its head and neck, and the manner in which adjoining
muscles diverge from one another should be noted. Fig. 4 gives the
deepest layer of neck-muscles, the shoulder-blade having been removed,
and Fig. 5 the immensely strong _ligamentum nuchae_, of yellow
elastic tissue, which extends from the base of the skull to the great
projecting spinous process of the lowest cervical and second and third
dorsal vertebræ.
[Illustration: Fig. 5.--Ligaments and tendons supporting the head and
neck of the horse.]
There are here indeed great forces for conflict--_first_ a layer of
strong superficial muscles, _second_ a layer of smaller muscles which
has not been figured, _third_ a deep layer of muscles, and _fourth_ a
powerful, widely-spread and strongly-attached mass of dense elastic
tissue, adapted for supporting the head without muscular exertion, but
by its elasticity allowing a downward jerk of the head and neck at
every step. It is an exceedingly important structure for a domestic
horse.
The Normal Arrangement of Hair.
So much for the active part played by a horse’s neck and head, and for
the simpler anatomical facts of the region involved. Before proceeding
to describe the results of these as seen in the hair, it is well to
make sure of a point which a critic might raise. “How do you know,”
says he, “that some of the variations in this highly variable region
of the hair are not normal. What is the normal type here?” A very easy
answer to this is found by studying, not only any Ungulate known,
except the Gnu, but more particularly all wild Equidæ; and this reveals
the fact that in all this series the normal slope of hair prevails
here, that is to say, an even trend from head to shoulder. Variations
in others, indeed, hardly exist, and I may add that the absence of
variations here is a strong piece of negative evidence in my favour,
for no Ungulate comes near the domestic horse for amount and activity
of locomotion, which is indeed his _raison d’être_. He is the only
one that has invented new patterns. But a little direct evidence
can be brought which clinches this argument from inference based on
ancestry. I made an examination, at the stables of Messrs. Tilling,
at Peckham, of 100 consecutive specimens of hackney, for the purpose
of ascertaining the proportion in that group of those that showed the
normal slope on the neck to those with variations. In 62 of these the
normal existed on both sides of the neck, 18 Normal on one side, and in
the remaining 20 there were variations on both sides. If 100 specimens
of horses contain 80 with one side and 62 with both normal the previous
inference requires no further support.
Fourteen Varieties.
I have put together here, and described, fourteen out of a much larger
number of the most instructive varieties of pattern that I have been
able to collect during the course of many years and examination of
several thousand horses. They comprise examples the mostly likely, as
I think, to convey to the reader an adequate picture of the results of
the strength, number and variety of mechanical forces in our present
battle-field of hair. The diagrams almost speak for themselves, but a
short written description will help to emphasise the salient points.
[Illustration: Fig. 6.--Side of Neck of Horse.
Normal type, hair-stream passing evenly in line of neck.--Bay hackney,
examined 3rd May, 1904.]
[Illustration: Fig. 7.--Side of Neck of Horse.
Complete whorl with wide feathering which extends from base of the neck
to the ear where it ends in a crest.--W.F.C.
Brown hackney, examined 12th January, 1904.]
[Illustration: Fig. 8.--Side of Neck of Horse.
Offside, anterior portion of neck showing line of division, B to A,
along upper border of sterno-mastoid muscle, normal arrangement from A
to C.
Grey pony, examined 15th December, 1903.]
[Illustration: Fig 9.--Side of Neck in Horse.
Near side, winter coat, showing normal arrangement from B to A, where a
division begins and extends along upper border of sterno-mastoid muscle
to base of neck.
Brown hackney, examined 28th December, 1903.]
[Illustration: Fig. 10.--Side of Neck of Horse.
Line of division of streams curving upwards to the mane near the base
of the neck.
Chestnut cart horse, examined 9th December, 1903.]
[Illustration: Fig. 11.--Side of Neck of Horse.
Near side, line of division along the upper border of sterno-mastoid
muscle diverted at C towards the mane.
Bay cart horse, examined 11th December, 1903.]
[Illustration: Fig. 12.--Side of Neck of Horse.
Near side, at C upward curve towards mane.
Brownish-yellow hackney, examined 18th August, 1903.
The same horse as appears in Fig. 13.]
[Illustration: Fig. 13.--Side of Neck of Horse--same specimen as in
Fig. 12.
Offside, fully developed whorl, feathering and crest W, F, C, lying
along upper border of sterno-mastoid muscle. Two stages of formation of
this form of pattern in one specimen.
Brownish-yellow hackney, examined 18th August, 1903.]
[Illustration: Fig. 14.--Side of Neck of Horse.
Near side, whorl (W) in place of common line of division, with wide
forward feathering to A, where the hair streams diverge sharply.
Brown hackney, examined 19th November, 1903.]
[Illustration: Fig. 15.--Side of Neck of Horse.
Near side, showing (B to C^1) diversion of hair stream towards mane
(W^1F^1C^1) whorl, feathering and crest; W^1 to W^2 stream in normal
direction W^2 a second whorl.
Chestnut cart horse, examined 1st January, 1904.]
[Illustration: Fig. 16.--Side of Neck of Horse.
Near side (W^1F^1C^1) showing whorl, feathering and crest along upper
line of division (W^2F^2C^2) a second fully-formed whorl, feathering
and crest, crossing both upper and lower lines of division, and
ending at W^1. Grey pony, examined 23rd May, 1903.]
[Illustration: Fig. 17.--Side of Neck of Horse.
Near side (W^1F^1C^1) whorl, feathering and crest, fully-formed,
cutting upper line of division at obtuse angle and a second whorl,
feathering and crest (W^2F^2C^2) along anterior part of common line
of division. Roan hackney, examined 7th November, 1903.]
[Illustration: Fig. 18.--Side of Neck of Horse.
Off side, simple whorl, behind ear at edge of mane.]
[Illustration: Fig. 19.--Side of Neck of Horse.
Simple whorl (W) at edge of mane midway between ears and base of neck.]
There are pictured here the normal type, divergent hair-streams
partially reversed, simple whorls in different regions, a whorl and
feathering, whorls, featherings and crests, and these in several areas.
It is a veritable portrait gallery in which is portrayed the earliest
and latest stages of this family of fashions in hair on the horse’s
neck. They are grouped mostly in pairs.
Fig. 6 shows the normal slope and by its side Fig. 7 gives a view of
the best specimen of a completed whorl, feathering and crest I have
been able to examine, _the whole length of the neck being occupied by
it_. So in this pair the normal and most extensive departure from it
lie side by side.
Fig. 8 shows the way in which two streams of hair close up to the ears
begin to diverge. Fig. 9 a similar divergence towards the base of the
neck.
Fig. 10 gives not only a divergence, but a well-marked turn in the
upper hair-stream and Fig. 11 the way in which this divergent turn of
hair is being converted into a feathering.
Fig. 12 presents a stream of hair still more twisted from its course
than that of Fig. 10, and Fig. 13 a whorl going on to a feathering
which loses itself, without coming to an abrupt stop in a crest which
is the more usual course.
Fig. 14 is a common type of whorl, feathering and crest in the most
usual situation. Fig. 15 a rarer and more complicated instance of a
simple whorl, a gap and then a whorl, feathering and crest in the same
“critical area.”
Fig. 16 and Fig. 17 are rare cases of irregularly placed double whorls,
featherings and crests, and give evidence of unusually complicated
traction of adjoining muscles underneath this battle-field of hair.
Figs. 18 and 19 show a simple whorl, situated at the very edge of the
mane, a very “critical” area because this looser and heavy part of the
neck is very much subject to jolting during the horse’s action.
I have little to add to the graphic evidence afforded by these
pictures, each of which I observed noted and sketched as the bearers
of them came before me during many years of a “Captain-Cuttle-like”
disposal of some of my leisure. No clearer proof can be desired of
the view here advanced, that habit or habitual muscular action, and
jolting, is the cause of the varied patterns in this field, and that
according to the Law of Parcimony no other is required, this canon
of Occam being expressed more succinctly--_Neither more, nor more
onerous causes are to be assumed than are necessary to account for the
phenomena_.
CHAPTER VIII.
CAN MUSCULAR ACTION CHANGE THE DIRECTION OF HAIR IN THE INDIVIDUAL?
It might seem unnecessary to most persons who are good enough to follow
this inquiry that the question asked above should receive an explicit
answer. We all know, of course, how a man’s hair is said to stand on
end in excessive states of horror or rage, and how a short-haired
terrier’s back bristles at the sight of certain foes. But it is not so
simple a matter to show that the direction of the hair is permanently
changed. I submit that the persons I mention are right in their opinion
for this work contains evidence throughout that muscular action beneath
the skin is the efficient cause in many regions of the formation of
hair patterns. But like Kirkpatrick when Bruce struck down the Red
Comyn we had best “make sicker,” and give as much evidence of the
affirmative question as any critic can demand.
Hairs of Human Eyebrows.
As in the previous chapter I chose an open and plain field for the
evidence bearing on the formation of whorls and the like, so here I
turn to one still more clear for him who runs to read. In these days
old men are of less account than in earlier and simpler times, but I
claim to have found “a new use for old men” as I had almost thought
of calling this chapter. In this somewhat neglected group we have an
almost unlimited number of specimens for examination, and in their
eyebrows they furnish a valuable field for tracing some striking
results of underlying muscular traction.
Darwin made one of his few mistakes when he included among rudimentary
and inherited structures[48] those few long hairs which are often seen
in the eyebrows of man, looking upon them as representatives of those
found in some species of macacus and the chimpanzee. That great and
modest man was, I am sure, not in the habit of making much use of the
looking-glass--not more than women who, as we know, rarely do such
a thing. But if he did he would have observed in his own splendid
frontal region and brows excellent examples of the phenomena which form
the subject of this chapter. This I know, though I never saw him in
the flesh, for it so happens that in the great volume published in the
jubilee of The Origin, and called _Darwin and Modern Science_, two good
photographs of him, at the ages of thirty-five and about seventy-one
are reproduced. These both show, but the later one much more clearly,
good examples of these long and not very ornamental aberrant hairs.
Thirty-five years of arduous thought and work had told their tale on
him and twisted from their normal paths the lengthening thickening
hairs of his eyebrows.
[48] _Descent of Man_, p. 19.
Also, if he had looked a little beyond the eyebrows he would have seen
some very deep wrinkles of the skin on his forehead and round his
orbits. It is these two groups of facts, wrinkles and twisted, changed
hairs of man’s eyebrows, which give the answer to the question “Can
muscular action change the direction of hair in the individual?”
In 1903 I drew the attention of the Anatomical Society of Great Britain
and Ireland to these two groups of facts under the title “Notes on
the Eyebrows of Man,” and presented some large drawings of individual
elderly men of my acquaintance, and the present chapter is only an
extension of that little piece of work.
No area of the mammalian skin is so useful and easy to follow as this
in answering the present question, for though the previous chapter
supplied part of the answer in a very fruitful field, the proof still
remained one of “tremendous probability” and not more. But in the
frontal and superciliary region of man there is complete proof of the
truth of the affirmative answer, as I shall show.
Here again we must encounter our old friend the normal slope of hair.
As I stated in 1903, “The normal arrangement of the hair on the
eyebrows of a moderately hairy subject is as follows: in the middle
line the hairs of the two sides tend to meet and form a somewhat
confused group of hairs; passing away from the middle line the hairs
assume a nearly sagittal direction, then become more sloped away, and
a sharp change in the direction of the _frontal_ and _orbital_ streams
brings the remaining hairs into that regular accurate arrangement of
a united stream so characteristic of a hairy subject, and this passes
along the superciliary ridge to the external angular process”--all of
which can be seen at a glance by any one who looks closely enough, as
with the eyes of a lover, for example, at the brows of a dark-haired
maid or youth. In the young these hairs lie close to the skin, and with
that very interesting group of persons we have no more to do here,
except for one piece of practical advice to them which they will find
at the end of the present chapter.
Evidence from Artists.
More than one kind of evidence may be brought forward in this case,
and I propose to “put in” a certain class of witness that not the most
acute cross-examining counsel, Daniel O’Connell, Hawkins, or even
Sergeant Buzfuz, can shake. I pity that young man or woman to-day who
has not mended several holes in his education by reading the books of
Dickens and Lever in editions illustrated by the immortal Phiz. If I do
no more for him by this passage than induce him to mend such holes I
shall have been of some use to his mind. For my part I look upon Phiz
as far superior to Hogarth or Cruikshank in the fidelity to nature of
his drawings of the faces of his numerous characters, especially the
old men. Look through _Dombey & Son_, _Bleak House_, _Pickwick Papers_,
_Barnaby Rudge_, _Tom Burke_, _Jack Hinton_, _Harry Lorrequer_, _The
O’Donohue_, and, perhaps best of all for the illustrations, _The
Knight of Gwynne_. Examine, with a lens if necessary, the delicate way
in which Phiz shows the projecting hairs on the eyebrows of his many
elderly men, and note at the same time the truth to scientific fact
which he shows in his _female_ characters, for only in the drawings
of “Mrs. Gamp proposes a toast” and of Mrs. Pipchin in “Paul and
Mrs. Pipchin,” and one or two doubtful instances, can I find that he
represents even his elderly women with this feature of their eyebrow
hairs. But see Captain Cuttle and Mr. Bunsby in “Solemn references to
Mrs. Bunsby,” both with strongly-marked shelves of hair sticking out
from the brows, Captain Cuttle in “The shadow in the little parlour,”
one of the fat coachmen in “Mr. Weller and his friends drinking to
Mr. Pell”--the sharp brush projecting from the brow of Bagnet in “Mr.
Smallweed breaks the pipe of peace,” that of Vholes in “Attorney and
Client, fortitude and impatience”--(the equally remarkable absence of
this feature in Pecksniff, Chadband and Skimpole, men without character
or feeling)--Gashford in “Lord George Gordon,” the fat figure in “The
Gallant Vintner,” Pioche in “Minette in attendance on Pioche,” the
courtier in “Louis XIV. and de Genchy,” “The death of Shaun,” the blind
man in “Joe the mighty hunter,” the right hand figure in “Mr. O’Leary
creating a sensation,” Sir Archibald Mc’Nab in “A fireside group,”
“Roade’s return to O’Donoughue Castle,” Sandy Mc’Grane and Old Hickman
in “Sandy expedites the doctor,” Daly in “Daly bestows a helmet on
Bully Dodd,” the knight in “The Knight is taken Prisoner.”
Another witness to the scientific facts of the frequent presence of
these hairs on the eyebrows of elderly men, and the rarity of them in
those of women, is the dear friend of our youth, our friend even to
hoar hairs, the _Book of Nonsense_, by Edward Lear. Here in 110 vivid
drawings of several hundred characters, each of them sketched with a
few bold strokes, is inscribed again and again this peculiar feature.
Look at the “Old man with a nose,” the “Old Man of th’Abruzzi,” the
“Old man of Melrose,” the “Old man of Calcutta,” the “Old Person of
Anerley,” the “Old Person of Chester,” all with strange and striking
bushes of long hairs standing out from their brows. Again see how
hardly one of the female characters shows a trace of it even in
that most truculent “Grandmother of the Young Person of Smyrna” who
threatened to burn her, though her vertical wrinkles are formidable,
or in the remarkable face of the wife of the “Old Man of Peru.” The
“Old Lady of Prague” shows it in a moderate degree. Support of this
kind may be trivial, and so will the opposing counsel say is that of a
burglar’s finger-prints, but, _quâ_ evidence, it is as strong as that
which commits the criminal to a prison on this modern proof. No one can
suppose that Phiz and Lear fifty or sixty years ago had a prophetic and
treacherous insight into the harmless labours of a man in the year 1920
who would exploit their labours to the advantage of his hypothesis,
and that they faked their caricatures for such a purpose. This is the
only alternative line for Sergeant Buzfuz to take unless he acknowledge
the facts to be facts, and betake himself to abuse of the plaintiff’s
attorney.
Eyebrows Interpreted by Wrinkles.
When one comes to the interpretation of the curious shapes taken by
these hairs one is not left to inference, for Nature has put some
indelible stamps on the forehead and round the orbits of the men
examined. These are wrinkles which have been long in preparation and
only begin to show themselves fully when the “evil days” have come, in
the ’fifties, ’sixties and ’seventies.
I will describe the wrinkles first, and then their results, with
examples, in the numerous fashions of the hairs. Wrinkles are of two
kinds, pathological and physiological, in other words the former are
the results of degeneration and wasting of the subcutaneous fat and
loss of its normal elasticity, and are found in the faces of nearly all
men and women, with advancing age, and they are the subject of much
distress in the fair sex and a good deal of “beauty doctoring.” The
latter are the result of long-continued and repeated action of certain
small muscles. The former are numerous, shallow and fine, the latter
few and comparatively deep. The difference between elderly women and
men in respect of the projecting hairs is not that men have many more
physiological wrinkles, but that the hairs of women in this region do
not stiffen and grow long nearly so much as those of men.
There are three groups of wrinkles found on the human forehead and
face, _vertical_, _arched_ or horizontal and _orbital_. This division
of wrinkles is a natural one, for each group is produced by the action
of different muscles, the _vertical_ by the corrugator muscle, which is
a narrow band passing from under the frontalis muscle inwards, where it
is attached to the bone between the two eyebrows; the _arched_ by the
action of the frontalis muscle, one which moves the scalp and in doing
so elevates the eyebrows; the _orbital_ by the elliptic orbicularis
muscle which closes the eyelids. These muscles are shown in Fig. 20.
_Vertical_ wrinkles are found in the central region of the forehead
and sometimes occupy the middle line with a deep furrow, more often
they are bilateral and symmetrical, near the inner fourth part of the
eyebrow, and sometimes they are placed at different distances from the
middle line.
_Arched_ wrinkles extend over the forehead in a series of lines
which are usually concentric with the curve of the eyebrows, but are
sometimes nearly horizontal.
_Orbital_ wrinkles may lie in a radiating plan all round the outer
lower and inner borders of the orbit, and in some persons they are
found lying over the curves of the orbicularis muscle itself.
Some Examples.
The variations in the long hairs of men’s eyebrows present some very
singular tufts, and I have added below nine figures of certain cases
examined and noted by myself, and these are, I hope, plain enough
without any more detailed account than is given in the few words
describing each.
Unless one’s attention be specially directed to these aberrant hairs,
which are extremely common, one would not expect that hairs could
be so variously twisted by muscular action beneath them. You may
see a tuft of long hair projecting from the plane of the eyebrows
towards the inner end, looking like a small horn, and I have measured
individual hairs in elderly persons and found many an inch in length
and a few an inch and a half. Such a tuft gives a fierce look to the
countenance if the hairs are bushy and plentiful. The celebrated Dr.
Keate, the flogging Head of Eton, a fiery strenuous person, was noted
for the extraordinary long horn of thick hair in his eyebrows, which
he appeared to use as a supplementary finger to point to this or that
object of his terrifying attention. You may also see a man with a great
drooping curtain of hairs overhanging his eyes, half hiding the upper
lids and eyes. Another will show at the outer end of the eyebrows a
bristling bush of hairs turning upwards in the aggressive manner of
Wilhelm II. of evil memory, or of Mr. Roosevelt in former times. Again
the outer points of the eyebrow hairs may turn downwards like a cavalry
moustache, or the hairs may stand out at right angles as a level shelf.
The fashions of these “orbital moustaches” appear to be as numerous as
those of the upper lip.
A Conflict of Forces.
If the eyebrows are studied in the light of the three muscles displayed
in Fig. 20 it is seen to contain an interesting congeries of small
forces in conflict. (1) The _frontalis_ moves the eyebrow directly
upwards. I had a friend once about seventy years old who was a very
vigorous, strong-willed man and he spoke with decision and energy. It
was most interesting to watch how his frontalis muscle strongly and
frequently contracted as he spoke and drew up his eyebrows so that one
might, as it were, measure the strength of his expressed convictions
by the rate of action of his _frontalis_ muscle! (2) The _corrugator_
draws the skin of the eyebrow inwards to the middle line thus acting
at a right angle to the line of the _frontalis_. (3) The _orbicularis_
in the upper part directly opposes the action of the _frontalis_ and
in the lower acts “on its own” in closing the lower lid. This little
spot is a Hill 60, destroyed at the battle of Messines, and has been
the scene of much fighting throughout life, and it bears abiding
witness in the twists and curves of the long hairs to the severity
of the struggles. These actions of the three contending muscles are
involuntary and of a reflex character, and much employed in such habits
as those of knitting the brows or in elevating or depressing them, all
this being set going and controlled by cerebral action. Incidentally
then the preponderance of one or more of these actions over others, as
shown in the hair, is evidence, as far as it goes, of the disposition
and character of the possessor. So that between the wrinkles and the
twisted hairs of his brow the elderly man, and less so the woman,
carries about an engraved statement, for his friends or enemies to
read, of his natural disposition and his acquired habits, in a limited
field--his written character!
[Illustration: Fig. 20.
Muscles surrounding orbit with lines of action. Left--muscles concerned
in movements of parts round orbits. Right--lines of action of these
muscles indicated by arrows.]
[Illustration: Fig. 21.--C. B. _æt_ 81.
_Hairs_: Thick and bushy eyebrows. At junction of outer and middle
third of each side the thick hairs turn abruptly downwards in a tuft
and cover the upper lid.
_Wrinkles_: Arched and lateral fairly well-marked, one very deep,
central and vertical wrinkle.]
[Illustration: Fig. 22.--G. W. _æt_ 79.
_Hairs_: On each side at junction of outer and middle thirds a definite
wisp of hair turning upwards.
_Wrinkles_: Arched and orbital well-marked, central wrinkles hardly
visible.]
[Illustration: Fig. 23.--F. F. _æt_ 57.
_Hairs_: Left side two long hairs from 1 to 1-1/2 inches long, turned
sharply up at outer end of eyebrow. Right side short hairs turned
upwards.
_Wrinkles_: Strongly marked, curved, orbital wrinkles round outer half
of each orbit. No other wrinkles.]
[Illustration: Fig. 24.--B. W. _æt_ 69.
_Hairs_: on both sides, projecting tufts at junction of the middle
and outer thirds of eyebrows, hairs an inch long. The outer fourth of
surface bare of hair.
_Wrinkles_: Vertical hardly visible. Arched wrinkles numerous and
especially deep towards the temporal region.]
[Illustration: Fig. 25.--T. R. _æt_ 57. Voluble talker, twitches
eyebrows in talking.
_Hairs_: Thick and stand out stiffly from eyebrows, turning slightly
upwards in outer third--almost absent from inner third of surface.
_Wrinkles_: Vertical faint; arched deep and long, equal on the two
sides, orbital, on each side two groups of deep radiating wrinkles,
beside many small lines.]
[Illustration: Fig. 26.--A. P. _æt_ 63.
_Hairs_: On each eyebrow at about the junction of the middle and outer
third, there is a remarkable tuft measuring 1 to 1-1/2 inch projecting
from plane of eyebrow somewhat upwards, scanty hair on outer third.
_Wrinkles_: Smooth open forehead, with moderate-sized arched and
orbital wrinkles. Vertical wrinkles hardly visible.]
[Illustration: Fig. 27.--G. G. _æt_ 54.
_Hairs_: Right eyebrow upward twist of hairs on outer half, left
eyebrow hairs lie straight; project, on both sides, well away from
plane of eyebrow.
_Wrinkles_: Arched on right side more numerous and extending higher
than on left. No vertical wrinkles.]
[Illustration: Fig. 28.--R. N. _æt_ 65.
_Hairs_: On right side hairs long and projecting nearly in horizontal
direction, on left sharply turned up at inner end and rather less so at
outer.
_Wrinkles_: on right sides, three faint arched wrinkles, one vertical,
short and small. On left, three deep arched wrinkles, one vertical,
deep and long.]
A Side-Issue.
This conclusion brings me to the piece of gratuitous advice I offer
to the unmarried reader. It will be more likely to appeal to the
woman than the man, I believe. Let such an one who is contemplating
matrimony make a short study of wrinkles and the long hairs if
possible--unfortunately she cannot do this of her prospective mate if
he be at all young, for neither of these features will be pronounced
as yet. I recommend instead a study of the wrinkles and hairs of the
father and mother and a deliberate summing-up of the evidence in this
way. If she wishes to have a cheery, genial, hopeful companion in
life like B. W. (Fig. 26) let her seek as many arched wrinkles in his
parents as possible and avoid very deep vertical wrinkles. If she be
herself of that disposition she will want a mate of different qualities
and may venture on one whose balance of family wrinkles inclines to the
vertical, _see_ Fig. 28, R. N. She can risk that, and perhaps get a
more capable and strenuous comrade in life’s battle. But let her beware
of him whose wrinkles are all of the vertical kind; for he will be
thoughtful, moody, abstracted and not too good-tempered. I would rather
myself join my fortunes to one who could claim a large share of arched
wrinkles.
[Illustration: Fig. 29.--B. F. _æt_ 52.
_Hairs_: On both sides much twisted downwards, producing shelf over eye.
_Wrinkles_: None on forehead; strongly-marked concentric orbital
wrinkles on both sides.]
After this digression, which follows logically on the facts and
arguments of this chapter I am now in a position to affirm that
_changes in the direction of the hair in the individual can be caused
by muscular action_.
CHAPTER IX.
HABITS AND HAIR OF UNGULATES.
Horses.
The Ungulate order has been variously divided by zoologists, and is
still said to be composed of two main sections, even-toed and odd-toed
Ungulates, with the addition of a good many “outsiders” if one may use
the term.
These sections form two sub-orders, and the division suits my purpose
here very well. I take the odd-toed sub-order of the Ungulata Vera
first.
Lessons from the Domestic Horse.
The domestic horse is the only member of this section that requires
detailed attention, and its value for studying the direction of the
mammalian hair is great, on account of the immense number of specimens
available, the quality and varied distribution of its hair, the size of
the animal, and, most of all, our intimate knowledge of its habits of
life for many thousands of years.
Many volumes have been written by man about this, his best and second
oldest friend among lower animals. His ancestry, his story as servant
of man, his virtues, strength, speed, intelligence, his use for war and
peace, his colour, varieties of breed and money value; his anatomy,
physiology, pathology, his medicine and surgery have all been written
by many able men. Indeed before the great revelation of what man can
be and do that the great war has given us, many observers of mankind
were prepared to adapt the saying of a French cynic and to declare:
“The more I see of men the better I like horses.” Swift at any rate
came near this in his bitter account of a voyage to the Houyhnhnms,
which lasted sixteen years and seven months, towards the end of which
he said: “For who can read of the virtues I have mentioned in the
glorious Houyhnhnms without being ashamed of his own vices, when he
considers himself as the reasoning governing animal of his country?”
But in all these writings, even in that last striking book by Mr. Roger
Pocock, _Horses_, little or no attention is given to the patterns of
its coat from the point of view of science. I remember reading a
paper on this subject many years ago before a distinguished company of
veterinary surgeons, and though they had glanced at these patterns in
a passing way, as peculiarities, no real knowledge of them nor attempt
to understand them was shown by this body of experts. They were too
“practical” for this view of things. I may remark here that many of the
most vocal and active among us, and especially the Germans, have been
overmuch disposed to study science _ad hoc_, for its commercial and
military value, though here, as elsewhere one must be tolerant and each
follow his own taste, seeking light, more light. One must live and let
live.
The horse does his work _coram publico_ in every street of every town,
in fields, roads and race-courses, and displays on his hairy coat some
graceful patterns which are at the same time subjects for scientific
inquiry, and brands of his long servitude to man. I have examined many
thousands of horses in some twenty years with never failing interest.
Belonging to the large family of Equidæ, including _asses_, _zebras_
and _quaggas_, he is the most highly-developed of them all. His habits
first, and then the most notable of his hair-patterns must now be
considered.
Some Habits of the Horse.
He has few habits which bear on the present subject, and of these his
active habits of locomotion are far the most important. He has his
share of passive habits, for he stands many hours a day, and often
sleeps standing, and he does his share in lying down, though Mr. Roger
Pocock says he takes no more than four hours’ sleep in this attitude.
His rule in lying down is to “lie anyhow,” if one may so describe it,
and thus his two passive attitudes of standing and lying, have little
or no bearing on the questions before us. His glory is in his gallop,
canter, trot and walk. His business is indeed a _going concern_ in
more than one sense, perhaps in three. The world is moving fast in its
old age, and some men are calculating how long it may take for him to
become as nearly extinct as the _quagga_.
With the clue given to this inquiry in Chapter VI. we need have
little difficulty in tracing the manner in which his locomotive life,
ancestral and personal, is engraved on his hairy coat. We shall bear in
mind the _primitive direction of his hair_, _hair-streams_, _lines of
least resistance_, and the powerful forces of _underlying traction_ of
muscles, opposed or divergent.
It is, of course, most convenient to examine a specimen with a
fine, short coat rather than one with its wild and more shaggy hair
remaining.
The two regions where the play of great forces comes most powerfully
into action during locomotion are round about the elbow-joint (which
we should be disposed to call the shoulder) and the hip-joint, in
which regions the range of extension and flexion, as well as the
number of muscles engaged, is much greater than at any other part of
the limbs. It is in the neighbourhood of these two regions that the
most characteristic of all the patterns of hair are found, and the
names given to the patterns (whorls, featherings and crests) in these
critical areas are _Pectoral_ (Fig. 30) and _Inguinal_ (see Fig. 31)
with a third (G, H, I, Fig. 31) which is called _Axillary_, and is not
constantly present. The main muscles involved in Figs. 30, 31 are shown
in Fig. 33. The _Frontal_ (Fig. 32) is another of the critical areas,
_indirectly_ concerned in locomotion, and will be considered first.
[Illustration: Fig. 30.--Front view of horse showing pectoral pattern
A, B, C.]
The _Frontal_ pattern forms the star on a horse’s forehead, often
very noticeable when the hair of it is white. No detailed description
is required if the illustration of it in Fig. 32 be studied. It is
enough to point out that it lies at or very near the level of the eyes,
sometimes a little above and sometimes a little below this, and there
is occasionally a double whorl, the second lying above the normal one.
[Illustration: Fig. 31.--Side-view of horse showing inguinal whorl,
feathering and crest A, B, C, and axillary whorl, feathering and crest,
G, H, I.]
Fig. 32A shows the muscles of the fronto-nasal region of the horse
and the manner in which the skin of this central region is pulled
upon in divergent and opposing directions, by a long muscle, called
the _Maxillaris_, downwards and outwards, by a small thick muscle,
the _Corrugator_, inwards, by a deeper and more oblique muscle, the
_Nasalis_, downwards and inwards, and a little more remotely by the
_Temporal_ muscle, and the _intrinsic muscles of the mobile ears_.
There are thus at least five muscles on each side, all pulling more
or less against one another on this much-disturbed area of skin. The
struggle has been long ago given up and a compromise arrived at which
is registered in the frontal pattern.
[Illustration: Fig. 32.--Frontal region of horse with frontal whorl
(_a_); feathering (_b_); crest (_c_).]
[Illustration: Fig. 32A.--Muscles of the fronto-nasal region of the
horse.]
Now if anyone doubts whether these comparatively small muscles act
often or strongly enough to produce effects on the hair over them he
need only consult Mr. Roger Pocock’s book to understand the story of
this battle of small forces and its result on the hair.
[Illustration: Fig. 33.--Side view of horse, showing chief superficial
muscles.]
In his wild state the horse is dependent to a remarkable degree
to his sense of smell for his safety from foes (Pocock), and very
much less so on his sight. Indeed that writer says his range of good
vision is about six yards. At that range his sight is of great value
to him for protection from certain of the dangers of his life, and we
see in a domestic horse to-day the evidence of his past wild life by
his rapid and keen glances at objects at the sides of the road, both
when we ride and drive him. His _corrugator_ muscle must be almost
constantly in action. But his sense of smell is the sling and stone
with which he encounters his Goliaths before they can get near him, and
he ceaselessly expands and draws up his flexible nostrils employing
his _nasalis_ and his _maxillaris_ for snuffing the air. He has also
much useful protection from his sense of hearing and we all know
how those mobile ears of his are hardly ever at rest, pointing now
forwards, now backwards, and again outwards, as he goes on his way. The
degree of these movements is largely a matter of individual character
and breeding. The case for a conflict of forces in this region is, I
submit, fully made out, and it is easy to see that a radiating pattern
of hair, such as there is in the simple whorl, is only the natural
outcome of all this complex muscular action. The extension of the whorl
upwards in the shape of a feathering which is sufficiently common,
indicates that the struggle has been carried beyond the original
battle-field by the muscles of the ears.
The _pectoral_ (Fig. 30) pattern lies over the great fleshy masses
formed by the pectoral muscles, which draw the fore-limbs upwards
and inwards in conjunction with others in the actions of flexion and
extension of these limbs. The patterns, A. B. C., are wide expansions
of reversed hair beginning in the whorl (A), extending (B) upwards
and terminated in a crest (C). This pattern is, like the frontal,
invariably present in a domestic horse, and is shared by many other
ungulates such as deer and antelopes, as mentioned in the appendix of a
small book[49], I published in 1901. But in none is it so striking or
definite as in the horse. The contractions of these pectoral muscles
and their jolt at each step are easily observed in a trotting horse. It
is interesting to compare this pattern on the horse’s pectoral region
with what is found on the closely allied ass and mule. In the horse it
is long and wide and never absent, and is especially well-developed in
high-stepping horses whether cart-horses or others selected because of
their high action in trotting. Its size, indeed, is a measure of the
activity of the pectoral muscles and flexors of the fore-limb. In the
ass it is often absent, and, when it is present, it is rudimentary;
in the mule it is more frequently present than in the ass, but
does not approach the pattern of the horse for size. These degrees
of development in horse, ass and mule correspond closely with the
locomotive habits of the three animals.
[49] _Use-Inheritance._ A. & C. Black. _Direction of Hair._
The _inguinal_ (Fig. 31) pattern is one which the most casual observer
of a horse cannot fail to notice, and it is so graceful in its shape as
to add to the many beauties of its possessor. But in spite of this no
breeder of horses has ever taken this pattern as one of the “points” of
the animal, so that here again selection, even of the artificial kind,
has had no share in its development. It is but a by-product of the
locomotive life of the horse, and a very ancient character, for it is
present in Przewalski’s horse, a probable ancestor of Equus Caballus.
A domestic horse without this pattern would be a freak of Nature. It
occurs in _equus hemionus_, the Thibetan wild ass, but not in _zebras_
or in the _quagga_.
The inguinal pattern deserves rather more description than the two
others. It is shown in Fig. 31 as A. B. C. and the muscles which
produce it and govern its development are shown in Fig. 33. It starts
in a whorl (A) at the fold of skin which passes from the lower part
of the abdomen to the hind limb. This radiates and expands into
a bilateral and symmetrical expansion shaped like the barbs of a
feather. This proceeds upwards in the inguinal hollow in a direction
which curves gently with the concavity forwards, dividing the trunk
of the animal from the great rounded mass of muscle forming the hind
quarters. It extends upwards to the level of the iliac crest where
a projection covered by muscles can always be recognised, and over
this “iliac crest” of the anatomist it terminates abruptly in a
ridge or crest of its own, lying parallel with the long axis of the
trunk. It is very pretty to see above it the hair-streams from the
back of the animal breaking away like two currents of water on either
side of an outstanding rock, the anterior passing with a wide curve
forwards and downwards along the flank and the hinder one losing
itself more gradually in the original course of the hair-streams of
the hind-quarters. No illustration or verbal description gives so good
a picture as one can get from inspection of the smooth coat of any
well-developed domestic horse.
When a few trotting horses are watched by an observer who bears
in mind the accompanying pictures of the muscles and the inguinal
pattern it can be seen at once how all the conditions are present for
fulfilling a gradual change from a primitive slope of hair to these
highly-developed patterns, if he has also followed the conclusion
reached in Chapter I. that _muscular action can change the direction
of hair in the individual_. If at the same time the degree and extent
of the jolt which occurs here at every step be noted, it is seen to be
sharply limited to the area covered by this pattern, and ceasing, as
it does, abruptly and significantly at the level of the iliac crest.
The forward range of the jolt, easily seen in a thin horse, is much
wider than the backward, and marks out very closely the extent of the
forward curve taken by the anterior hair-stream as it descends from
the crest. One may also remark that there is a small but interesting
point which one can see during or after a shower of rain, for then the
flank of a horse presents a curious distribution of the moisture. At
the very point where the forward stream joins the main stream from the
thorax and abdomen a definite line of darker moist hair is to be seen
and the moist-looking surface is limited to the stream of the trunk
and separated from that of the flank. This line of demarcation clearly
indicates the place where the _forward jolt_ terminates during rapid
movement.
The Domestic Ass and Mule.
There are two closely related animals, the domestic ass and the mule,
which ought to show this inguinal pattern if affinity and variation
could be fairly invoked to account for it on the theory of selection.
These are also animals whose mode of life is locomotive, but in a much
less degree than the horse and their paces are quieter and less free
in character. What then is found in them as to the size or persistence
of this pattern? In the ass it is absent or nearly so (I have found
one example of its presence), and in the mule it is variable and never
occupies more than half the area of that in the horse. These facts
agree closely with the hybrid character of the mule and the differing
activities of the horse, mule and ass. The pattern in Przewalski’s
horse is small and oval and resembles that of the mule. The _onager_
(_equus asinus_), which is very much like these three domestic animals
in form, has an inguinal pattern, much less in size indeed than that
of the horse, but well-defined, and this fact is in keeping with its
character for remarkable fleetness of foot and activity. The three
zebras, Mountain, Grevy’s and Burchell’s, show no inguinal pattern,
in spite of their _power_ of rapid locomotion and resemblance in size
and form to the horse. Though they have that power they exercise it in
their wild lives for their own sakes alone, in the intermittent way
which is bound up with their habit of life, and not for the sake of
man, as in the case of the horse.
The pectoral and inguinal regions of the domestic horse are two of
the most valuable fields in the mammalian body for studying the
formation by muscular action of patterns of hair, for this animal is
the locomotive animal _par excellence_. Here the process has been
carried to the extreme limit, and these two are prominent examples
among the characters to which I drew attention in a paper published in
the _Proceedings of the Zoological Society of London_, “On proposed
additions to the accepted systematic characters of certain Mammals,”
June 9th, 1904, Vol. I. I am still of the opinion that they deserve
“Flag rank,” though they have not yet been promoted. Be that as it may
I think it may be well here to compare two animals belonging to the
family Equidæ, the horse and zebra, which resemble one another very
closely in form--in respect of these patterns.
Horse and Zebra Compared.
If a horse of the hackney type and a zebra were skinned and the bodies
of the two animals then examined I suppose a competent anatomist
would find some difficulty in distinguishing one from the other so
closely do these two allied species of equidæ, one wild and the other
domesticated, resemble one another in structure. But in this as in many
other questions _form_ is not to be considered alone. The colouration
of the two animals is strikingly different, but, in its humble way,
the difference of their patterns of hair-arrangement is worthy of
notice. The horse in different specimens chosen from a large group
will exhibit patterns in the frontal, pectoral and inguinal regions
constantly, and variably in less common regions, axillary, cervical
and gluteal, that is to say, in six different areas. I have examined
many zebras, living and dead, and find no constant pattern in the whole
of its large surface of skin except an ill-developed frontal and a
very small cervical one--_two in all_. The mere numerical difference
is not the only important one, for the insignificance of the size of
the two zebra patterns and the constancy and high development of many
of those of the horse are not less significant from the present point
of view. I submit that these two animals carry about with them on
their hairy coats indubitable records of their personal and ancestral
habits. Attention to the facts of a horse’s life and certain related
and contrasted facts of the lives of other animals, of which the zebra
may be taken as a type, will show the reasons why these patterns are to
be looked upon as registers of long-past and present activities of the
species concerned. The horse has been developed out of a wild plastic
stock with some such ancestors as the wild horse of Przewalski, lately
brought to Europe, by a process of selection by man during a thousand
generations, first in its Central Asian cradle and later all over the
civilized world. It has been as much _made by man_ for his purposes in
locomotion as a locomotive engine has been made by him. The one has
been produced in accordance with the laws of applied physics and the
other by those of biology. His locomotive life has come to pass for
the needs of higher, or at any rate more cunning creatures, who have
availed themselves of the potentialities provided by Nature. The zebra
in its habits differs from the horse in the simple, but fundamental
point that the former lives the ordinary active life of a wild animal
for its own needs of protection against foes and search for food, the
latter has not only this activity of life in its organisation, but has,
super-added to it by domestication, all the locomotive life of a beast
of burden. The zebra presents few, if any, of those phenomena which I
have often termed Animal Pedometers,[50] so characteristic of the hairy
coat of the horse I am reverting here again to the region of metaphor
for which I offer no excuse, but only a few remarks as to the use and
value of that elusive method of illustration. Metaphor is a figure of
speech or writing which consists in a transference of thought from
one idea to another. It is, therefore, not a simple substitution of
synonymous expressions, nor is it merely a simile. It is in hourly use
in the speech and writing of common as well as highly educated persons,
and adds much to the ease of communication among us of our thoughts
upon subjects which rise somewhat above the level of mere statement of
obvious facts. So long as metaphors are not abused by being used as
arguments to prove some proposition, but only as illustrations of our
meaning, we gain greatly by their legitimate use. It is not for nothing
the well-drilled Press of Germany in their journals and its histrionic
Emperor in his rhetorical outbursts, make extensive use of metaphors.
We are everlastingly reading of Germany’s “biological necessity,” her
“iron will to victory,” the “steel ring of field-grey heroes who guard
her against a world of devils,” of her “brilliant second,” her “granite
walls,” her “future on the water,” the “Admiral of the Atlantic,”
“grasping the trident,” and so on in nearly every public utterance of
her leaders. They know well their audience and employ these harmless,
if often ridiculous, expressions with a definite and legitimate
purpose, and are well qualified for creating the public opinion of a
nation that dearly loves a phrase.
[50] _Knowledge_, January, 1903.
Well, this term, Animal Pedometers, is used here not for proving
anything, but for the purpose of impressing on the mind of the reader
the fact of certain patterns on the horse’s skin being intimately
related to its locomotive life which, I hope I may assume, has been
sufficiently demonstrated in this chapter. A pedometer is one of those
works of men devised for his physical and mental advancement which are
marked by a precision as well as purpose often absent from Nature’s
handiwork. Just as a pedestrian, cyclist, or motorist carries with
him his pedometer and tells you with some pride the number of miles
he has “done” in a day or hour, so the horse displays _urbé et orbi_
his rougher registers of the locomotive triumphs of his ancestors and
himself, and these I call Animal Pedometers by way of metaphor, and
patterns by way of fact.
The less striking and rarer patterns of the horse’s hair have been
fully described elsewhere,[51] and it would serve no useful end to
refer to them at length, nor to multiply proofs of the position here
maintained.
[51] _Direction of Hair in Animals and Man._
CHAPTER X.
HABITS AND HAIR OF UNGULATES.
Oxen.
The even-toed section of hoofed animals is a much larger group than
the odd-toed, and the difference may be illustrated by looking at the
great work on Natural History by Lydekker. There are 273 pages given
up to this group and only 112 to the odd-toed, and when we remember
that there are contained in it the hippopotamus, all the pigs, oxen,
sheep, goats, antelopes, camels, llamas, giraffes and deer, we can see
that Lydekker was well justified in the great amount of space devoted
to them. But we all have our different forms of _penchant_, and I
propose to say very much less about this section than about the other
represented by the domestic horse. It is well to claim the shelter
of a great name in such an apportionment of interest, and Professor
Poulton has given a clear precedent in his great book called _Essays
on Evolution_. It contains 393 pages and even though the subject of
the work is Evolution, he has given up 330 pages approximately, or
five-sixths, of his space to insects. This can be gathered from a rough
analysis of his various essays, and no one need blame a great biologist
for having a _penchant_ for the subject he knows best, or a small one
for writing of that he knows a little.
The reason that the even-toed ungulates require less study from the
present point of view is that they are so much more marked by the
normal or primitive slope of hair than the previous group of Chapter
IX. They demonstrate very widely and thoroughly the empire of the
primitive or “barbarian” forces and so far are valuable witnesses of
the negative kind. No case can well be proved to satisfaction by a
large series of negatives, and this was the hopeless task Weismann set
out to prove, when he staked his all on the non-inheritance of acquired
characters--and failed. But negative evidence is of great value in
supporting an hypothesis when it is found to be the precise complement
to extensive positive evidence brought in favour of that hypothesis.
That is the case in regard to the patterns of hair found on oxen,
sheep, antelopes, gazelles and deer, to say nothing of hippopotami,
pigs and llamas. There are some of these patterns described in the
previous group which appear in this larger one, but for size,
persistence and frequency they cannot be compared to those of the
horse, who has, if I may so say, inherited all the family property in
his own person and added to it.
The variations in the present group are fully dealt with in the two
earlier books already quoted,[52],[53], and I will not complicate this
chapter by any further remarks on them.
[52] _Op. cit._ _Use inheritance._
[53] _Op. cit._ _Direction of Hair._
Oxen.
Of the numerous divisions of even-toed ungulates the oxen present the
best cases for study of the various ways in which the hair is disposed,
and among them the best as well as the most accessible is the domestic
ox. Again we have a familiar friend of man and innumerable specimens
for examination as in the case of the horse. So this chapter will, like
the preceding one, resolve itself into the study of one typical animal,
with whose habits of life we are intimately acquainted.
Before describing the habits and hair of the domestic ox or cow, I
would like to point out why I value so highly the negative evidence
which consists in the comparative rarity of whorls, featherings and
crests in even-toed ungulates. This brings us back to the general fact
of the _raison d’être_ of the horse and his group on the one hand,
and the ox and his numerous relatives on the other. There are deer,
antelopes and gazelles which for a spurt would beat any horse and even
the Thibetan wild ass, so I am not trying here to disparage the power
of this graceful swift group in the matter of sprinting. But this term,
however colloquial it may be, clearly marks off the powers and habits
of deer, antelopes and gazelles from those of the horse, for, except
when trying to escape from an enemy, no deer, antelope or gazelle
is fool enough to sprint or even trot for mere pleasure or want of
occupation, and certainly not in the service of man. Thus it comes to
pass that animal pedometers are few and small in this second group of
ungulates, and I submit this negative fact gives strong support to the
views advanced throughout this volume.
A Cow’s Habits.
A cow is a very restful animal except when disturbed by extraneous
causes, and the active habits of her life are of little interest here,
the chief importance of her for study being the passive side of her
life or small minor tricks. As a domestic animal she lives to eat--and
be eaten and drunk--but her wild ancestors and relatives have had far
from an easy life, though this (in them even) has not expressed itself
in animal pedometers. But on her neck, back, flanks, legs and haunches
the cow has some interesting specimens of areas where the normal
hair-slope is reversed in accordance with her habits.
The most striking of these is shown in Figs. 34 and 35, where the
bare form of the animal is shown and the dark thick arrows are made
paramount in order to make the remarkable arrangement of her hair along
the back so clear, that little verbal description is needed.
[Illustration: Figs. 34 and 35.
(A) Side view of cow, showing arrangement of hair-streams on the back.
(B) View of back of cow, showing the same.]
Behind the level of the horns the normal or backward slope proceeds
until the middle of the length of the neck is reached, when it
encounters transversely a sharp upstanding crest and beyond this the
hair is directly reversed from a point over the shoulders, and here
a whorl is found. From this point the stream returns to its ancient
and normal course and so passes to the tail. When the base of the tail
is reached a very significant and apparently whimsical arrangement of
the hair down the centre of the tail is observed. This consists in a
line of stiff hairs which stand up at right angles to the surface of
the tail, and it gradually passes into the normal again when the more
muscular part of the tail is passed. I should add here that the crest
and reversed hair on the back are common to many wild ungulates of
this ruminant group, and a good example of it is seen in an antelope,
Oryx Beisa, which I figured and described in a paper at the Zoological
Society of London.
Arrangements of its hair so audacious as these need explanation, and it
is found in the mode of life of the cow. So large a part of its daily
life is spent in the business of grazing with her muzzle close to the
ground, during which the neck of the animal is constantly stretched
downwards from the back at the level of the shoulders, that the skin,
which is very loose in this and most other portions of its body, is
dragged upon to allow of the extreme flexion of its neck. This traction
is for all this time acting against the normal or backward slope of
the hairs, and has given rise to this victory of a new force through a
thousand generations. It is equally clear that a mechanical explanation
of the line of erect hairs on the first nine or twelve inches of the
tail is forthcoming, for one has only to watch a cow standing on a hot
day, undergoing her torment of flies, to see it writ large. Very strong
little muscles are found at the base of the tail, those along the more
free portion becoming smaller and smaller until they disappear towards
the tip. These give a powerful flicking action to the long heavy tail
and I once made some observations as to this on a number of cows which
were grazing in summer on a comparatively cool wind-swept hillside
in the western end of the Isle of Wight. I watched several cows on
different occasions and found that one would flick her tail 348 times
and another 1082 times per hour. Giving these cows an eight hours’
working day, “working” for their living in grazing and ruminating by
turns, one gains a vivid idea of the number of times per diem these
powerful muscles of the tail contract. If we call it a day of four
hours of grazing and four of ruminating, for the sake of argument, we
get 1392 to 4328 flicks of the tail each day in the time of flies,
leaving out of account the casual flicks in which she would indulge
when flies were not tormenting her. It is hardly necessary to point out
how the underlying muscles would drag upon the skin of the tail over
them and gradually reverse more or less the “lie” of the hairs. They
have not formed into a feathering or complete reversal, but have come
near to it.
Further down the haunches of the cow there is on each side at the back
of the thigh a curving reversed area of hair which turns upwards and
towards the middle line. This is the place where the tail as it swings
from side to side sweeps over the limb and brushes upwards the hair of
the thigh towards which it is swinging. So that the activity of the
tail is responsible for another of the patterns in which the cow’s hair
is arranged.
The lower segment of the hind leg exhibits one more reversed area of
hair due to the cow’s habit of lying on the ground slightly inclined to
one side, for the more comfortable disposing of her limbs, the effect
of this attitude being seen in the manner in which the hair on the back
of the leg turns inwards.
On the dewlaps and flanks are certain variable curls and turns of hair
produced by the frequent twitchings of a muscle situated just under the
skin called the “Fly Shaker” or _panniculus carnosus_. This muscle is
seen any day in the carcase of an ox hanging up in a butcher’s shop,
and it is interesting to notice the fact that it is distributed over
only the lower half of the flank, for the purpose of shaking off flies
from a region which the tail does not reach efficiently. None of this
sheet of muscle is found within the effective range of the cow’s light
artillery, as on the haunches or hinder portion of the spine. This sums
up the equipment of patterns of hair on the species of this group of
ungulates, which is more adorned with them than any I have examined,
and it will be admitted that compared with those of the horse, it
is a poor exhibition, but one which it is easy to understand if the
fundamental principles of this inquiry are kept in mind.
Light Occupations of the Cow.
I watched lately a little act of this drama among a herd of cows on
the Stray at Harrogate during a hot day. There were 105 of them and
this was what they were doing all day--some were browsing with their
muzzles close to the ground, their necks making a considerable angle
with the line of their trunks, others standing stock still with their
heads raised at a level with the body, gazing vacantly into space,
others lying on the grass more advanced in the strenuous work of their
day, ruminating with head level, also gazing at nothing in particular,
with their bodies gently rolled to one side, their fore legs doubled
straight under them and their hind legs planted to one or other
side, and a fourth group still nearer the end of the cycle of work,
lying with their chins resting on the ground. When this cycle was
completed the stages would again be begun, continued and ended. They
were flapping their wide ears in various directions, and twitching
endlessly the skin of the flanks and dewlaps with their fly shakers.
This large group afforded, if one may so describe it, a cinematographic
picture of the lives of countless generations of this conservative
animal. Conservative as she is, I doubt not that in the long-past
ages her quiet though persistent habits had once a battle to wage for
the production of even these mild innovations that I have described.
These present fashions must have been well developed three thousand
five hundred years ago and have adorned that “calf, tender and good,”
which Abraham in the plains of Mamre fetched for the midday meal of his
visitors.
CHAPTER XI.
HABITS AND HAIR OF CARNIVORES.
Cats.
Another large and important order of hair-clad mammals must now be
considered, and the same course as in the case of the ungulates will be
followed; the two leading families of Felidæ and Canidæ will be taken,
and a type of each examined in reference to its hair-distribution.
Lydekker gives about 100 pages to the cats and 80 to the dogs, so from
the point of view of general biology there seems little to choose
between them. The bears, racoons, weasel tribe, seals and walruses may
be put out of account. They are painfully old-fashioned or Normal as to
the arrangement of their hair.
First things first is always a good rule, and there is little doubt
where we ought to begin among the families and species Carnivores.
Among Felidæ one cannot unfortunately choose the harmless necessary
cat of tiles, areas, firesides and ladies’ laps, to say nothing of
those lovers of cats like Huxley who would never eject his cat from
his armchair if she had been there before him. It is true that we know
much of her daily and nightly mode of life--many of us too much--and in
that respect one could set to work with confidence in interpreting her
hair patterns, but on account of her long and thick coat we can only
speculate what patterns or innovations of her family uniform she might
have devised; but here we are not concerned with romance or the “might
have beens.” It will be remarked that one perforce unconsciously calls
the domestic cat “she” as sailors do their ships. I understand that in
Somersetshire they call everything of their common life “he” except
the tom-cat who is always “she.” The reasons for the use of genders in
different creatures would be an interesting little study.
Lion.
The King of Beasts will, therefore, be the hero of this chapter.
Lydekker tells us that the lion, like many heroes of antiquity who are
no heroes to their valets, in spite of his character for grandeur,
nobility and courage, has been subjected to the merciless higher
criticism of modern travellers, Selous, Livingstone, and others, and
he has been shown up as cowardly by nature and mean in his general
conduct. It remains for some learned scholar to whitewash the hyæna, as
someone has done for Caesar Borgia, and to put him in the place of the
lion. But Lydekker does not admit that this disparagement of the lion
goes very far. He _is_ the King of Beasts by grandeur of appearance,
strength and ferocity.
[Illustration: Fig. 36.--Lioness, showing by arrows the direction of
hair-streams on muzzle, parting from one another at the level of the
orbits.]
The lion’s skin is covered by close fine hair, except in certain
seasons in cold climates, and is easily studied. There are three
regions where this representative cat has departed from the Primitive
mammalian slope of hair, and the figure of a lioness shows two of
these, the peculiar _downward_ trend of hair on the muzzle and the
whorl on the shoulder. Fig. 37 shows the third, A C, on the middle of
the back as well as the whorls at D.
Snout of the Cats
The muzzle of all the cats is very short and broad, and at the level
of the orbits shows a peculiar reversal of the hair from the rest of
the head, for instead of being like that of a dog in which the hair
slopes all the way _upwards_ from the tip of the snout to the rest of
the head, it breaks away from this normal type and passes in a uniform
close stream to the edge of the wet muzzle. The arrows in Fig. 36 show
this change. One asks at once the reason for such an unexpected trend
of the hair on a small area, when the carnivores in other groups have
a uniform slope towards the head from their more pointed muzzles. The
cats have discarded the earlier family pattern and for a reason which
does credit to their self-respect. Very few naturalists know, or have
described so well the meticulous care which animals take of their
coats, as Miss Frances Pitt did in the _National Review_, where she
gave a delightful account of “How Animals Clean Themselves.” The toilet
of the lion she did not discuss, perhaps for prudential reasons. Her
account dealt chiefly with a number of small hairy mammals and lower
forms of life. Watch a dog cleaning his coat and you will see the
ingenious way in which he pushes his head and body forward as he lies
on some rough surface such as grass, or our best drawing-room mat. _He_
can thus clean his snout and other parts, but no cat adopts so rough
and ready a method. We know how long and how scrupulously she licks her
fur to clean it in the parts she can reach and cleans her head with her
paws. But with such a broad snout as she and the larger cats possess
she cannot clean the short surface of it in the manner of the dog. So
she “dresses” this little surface in a special way of rubbing it from
the neighbourhood of her eyes _forward_ with her paws. And so we may
assume does the chieftain of her clan finish off this little bit of
his toilet. We are so much accustomed to dwell on the naturally clean
habits of a domestic cat that without such an account as Miss Frances
Pitt has given we should have hesitated to transfer the character for
personal cleanliness from the domesticated to the wild cat. If this be
not the sole reason for the course of the hair-stream I have described,
I am at a loss to imagine any other.
Lion’s Neck.
On each side of the lion’s neck where it joins the shoulder there is
a well-developed whorl, and this as a rule is extended forwards into
a feathering (Figs. 36 and 37), and ends in a crest on the lower part
of the side of the neck. It is common also in tigers and leopards.
This is, as elsewhere, a record of strong and oft-repeated action in
powerful muscles which lie beneath it, and bears witness to the great
functional activity of the fore-limbs as compared with the hind-limbs
in these three formidable cats. It is not an animal pedometer, but may
perhaps be termed an _ergograph_.
[Illustration: Fig. 37.--Back of Lion, showing reversed area of hair
with whorl at A. Feathering B. Crest C.]
Lion’s Back.
The strange pattern of reversed hair (Fig. 37) is much the most notable
of the three peculiarities found on the lion’s skin. It consists of a
whorl (A) lying over the lumbar region in the middle line which expands
into a very broad feathering (B) and terminates in a crest (C) a short
distance behind the level of the shoulders. This is not found in any
of the numerous short-haired Felidæ that I have examined, and it is a
feature which demands explanation. I know no other mammal, ungulate or
carnivore, that has any pattern resembling this; indeed, if one were
to photograph the pattern in question and a few inches of the skin
surrounding it, and be told that it came from the back of a mammal
one could not doubt that it was a hall-mark of the King of Beasts. It
would not produce that thrill of intense interest which we felt at
the meeting on 7th May, 1901, at the Zoological Society of London,
when from a water colour sketch and three pieces of skin taken from
the body of a hitherto unknown mammal, Sir Harry Johnston proceeded
to reconstruct the Okapi, at first dubbed knight, as a member of the
Equidæ, but later promoted downwards to the Giraffidæ. But one could do
no less, with some knowledge of the hair of mammals, than reconstruct
from such a photograph a large, powerful and ferocious carnivore, and
where but in the lion can the greatest example of those attributes be
found? I say this advisedly, for this remarkable pattern of the lion’s
back is as much a stamp of his moral or mental quality as the Inguinal
Pedometer is of the locomotive _rôle_ in life of _equus caballus_.
I hear the sharp voice of the critic here, “Come, come, you may have
shown reason for the latter, but how on earth do mental and moral
qualities of an animal come into your scheme?” Well, we have in this
pattern of the lion’s back to deal with a unique phenomenon for the
production of which neither pressure, nor friction, nor gravitation,
nor underlying muscular traction will account. Nevertheless, it is
a result of muscular action of a rare kind. Who does not know the
striking appearance of the hair along the centre of a short-haired
dog when he bristles up with rage or fear, or both combined, at the
sight of a foe? This common event has its own mechanical cause, though
it is one strictly governed by the mental and moral qualities of
the dog, and we see the vivid proof before us of the action of the
minute _arrectores pili_, in this particular region of the dog. It is
precisely in the same situation that the special pattern of the lion’s
hair is found. It is not for nothing that Nature has provided every
tiny hair of the mammalian skin with that insignificant little band of
muscle which lies within the hair-pit, and is attached to the sloping
hair on its posterior side, and thus when it contracts serves to drag
it into an erect position. I refrain from discussing what may be held
to be the survival value, under the theory of selection, of this power
of the _arrectores pili_ to confer on the possessor an added appearance
of ferocity and general frightfulness. This is quite a likely
explanation of the presence of these little muscles. Be that as it may
the _modus operandi_ of the reversed hair which has become fixed on the
lion’s back is made clear, theory of origin apart. And I submit that
the presence of it in this region in this animal _is_ a stamp of his
persistently ferocious nature, as much as the various peculiarities of
arrangement of hair on man’s eyebrows in a previous chapter are of the
mental and moral habits of the individual man. As rulers of old used,
in their genial fashion, to brand a supposed or actual criminal on his
shoulder or forehead, so is the lion branded with an hereditary mark of
his nature and the past life of himself and his ancestors. I doubt not
that if short-haired terriers were living a wild life among numerous
foes their bristling hair would have become fixed in a similar fashion.
I would only here draw the attention of the reader to the fact that
this reversed area of hair on the lion’s back cannot be held to add to
the general frightfulness of the possessor. It would be invisible to
an approaching foe, as it lies hidden behind the great head and mane.
This pattern on the lion’s back will be referred to later in a somewhat
different connection.
CHAPTER XII.
HABITS AND HAIR OF CARNIVORES.
Dogs.
Among the canidæ one is able to select a type with whose habits of
life we are more familiar than any other, Canis Familiaris, as he is
affectionately called, the companion of man his master, and faithful
guardian--often unto death. Professor Scott Elliott gives reason to
think that the dog was the first animal tamed by man, and that he was
descended from some wild jackal-like form, probably crossed by the
wolf. The dog is then aptly called by Huxley, the brother of the wolf,
who has been changed by the intelligence of man into the guardian of
the flock. It seems that in his rudimentary stage of domestication he
was an unofficial scavenger among the habitations of neolithic man,
as the pariah is in the East to-day, and that little acts of kindness
towards his offspring on the part of those early men and women were
the first dawnings of a friendship of thousands of years. It is a long
story from the slinking jackal to the bloodhound, mastiff, St. Bernard,
staghound, collie and terrier of to-day, and one which reflects much
credit on both parties to this friendship, just as do those other
long friendships between servant and master, of which we still see
a few examples. Living with us as he does the dog and his habits
of life are an open book: he is then all the better for my humble
purpose here. I would refer again to the curious use of the gender
which we unconsciously apply to the dog. It is no longer “she,” but
“he.” When a dog is looking a little unfriendly how we always try to
wheedle him with “Poor old fellow,” and so on, as a matter of course,
assuming his masculine character. James Payn pointed out once a little
point which proves how good a comrade we have in the dog, when he
reminds us of the cautious approach we usually make to a cat, and the
“hail-fellow-well-met” tone we adopt towards the dog, rolling him over
and using kindly opprobrious terms, such as friends among schoolboys
hurl at one another when they are on the best of terms. A fox-terrier
is, perhaps, the most human of all the numerous types evolved through
the skill of man, and it is a smooth-coated specimen of this variety
which I will examine now as to what his hairy coat can tell us of his
habits.
Some of the Dog’s Habits.
His attitudes which bear on this question are all of the passive order.
His locomotion is so fitful and different from that of the horse that
we shall find on his coat no animal pedometers.
[Illustration: Fig. 38.--Gluteal region of dog, showing whorls over the
tuberosities of the ischia.]
His passive attitudes consist of standing, sitting and lying. He stands
little, sits more, and lies for a great part of each day. The standing
habit has, of course, no influence upon his hair. In sitting he rests
the chief weight of his body on the rounded, bursa-covered surfaces of
his tuberosities of the ischium, in which there is nothing peculiar to
himself. His fore legs are planted nearly upright on the ground and his
hind legs doubled under him or projecting slightly to one or other
side, as we saw in the case of the cow. The fore legs are obviously
in no way affected as to the direction of the hair in the sitting
posture, and the hind legs, being doubled up and subject to the direct
downward weight of the body, are also free from the _sliding pressure_,
which we shall see affects the fore limb when the dog lies prone. Thus
of the three supports, fore legs, hind legs and tuberosities of the
ischium, two are necessarily unaffected in their patterns of hair. The
anatomical conditions of his tuberosities are very different in this
respect. They are covered with a large slippery bursa just beneath
the thick skin, and the slightest movement of this alert and restless
animal, even of his head, conveys to this region a small change of
position. He is virtually like a sick person on a water or air cushion,
and we all know how very small movements of the body are felt in a
slight stirring of the supported parts by these. The effect of this
is that the hair over these bursæ is seldom at rest from external or
extraneous forces, to say nothing of its own imperious constant growth
of one inch in two months. In Fig. 38 one sees the hair-stream curving
round the buttocks towards the region of these bursæ, and trying to
reach the middle line. It meets with so much opposition that the very
conditions for producing a reversed area are present and the result is
just what one would expect to find. The pattern is formed exactly over
the bursæ limited to this area, and it does not expand anywhere because
there is no need for it to do so. So when one observes on the surface
just below the tail a pattern, often in a black-and-tan terrier marked
by a tan patch of hair, one reads the record of the long time spent by
the dog in sitting as he meditates on some fresh or past escapade of “A
Dog’s Day.”
The statement just made that the hind leg does not share in the effects
of pressure is not strictly correct; it applies to the _leg_ properly
so called. But the upper part of the thigh exhibits a very clear
reversal of hair due to the weight of the body acting here against the
streams from the side of the thigh, which are seen endeavouring to make
their way to the inner side. They are arrested by a long ridge of hair
which marks the obstacle presented by the weight of the body acting
here. This completes the story of the way in which sitting affects the
hair of the dog, and is shown in Fig. 38.
Lying Attitude.
[Illustration: Fig. 39.--Foreleg of domestic dog, showing reversed hair
on under surface, which rests on the ground in lying posture.]
[Illustration: Fig. 40.--Showing chest of domestic dog, with reversed
area of hair on each side.]
There are four attitudes adopted by the dog in lying. In the first,
when he sleeps he lies stretched out on his side on some surface, with
his limbs projected nearly straight out, and in the second, he curls
himself up in _his_ armchair in a cosy, rounded posture. But in both
these attitudes there is no such sliding pressure as will affect in
any way the direction of his hair. In two other favourite attitudes
it is far otherwise. When he lies prone he plants his fore limbs out
before his chest and either raises his head to the level of his trunk
or rests it on his fore paws. Each of these attitudes contributes to
a very well-marked change of the hair on the under surface of his fore
arms, to use a convenient human term, one which carries us back to the
story of man and the apes when their fore arms were discussed. On this
surface, from the mechanical conditions involved, a new force, that of
_sliding pressure_, comes into play. The skin here is very loose, as
indeed it is in the greater part of his body, which may almost be said
to form one large subcutaneous bursa. The weight of the fore part of
his body and head acts _downwards and forwards_, and thus opposes the
normal or downward course of the hair on the limb, such as one sees on
the upper surface of his fore arm. The resultant of these two forces
has the effect of acting against the normal slope, and a reversed
direction of the hair is produced very much like that which is seen
in many monkeys and in a small area in man. This is shown in Fig. 39,
which appeared in the small book[54], to which reference has been made,
and it is confined to the part of the limb where the sliding pressure
is seen to act. In this feature again there is a record of his resting
habits, and, of course, the time he spends in the fourth attitude with
his chin resting on his fore paws contributes its share, the mechanical
conditions being similar.
[54] _Use-Inheritance._
This fourth attitude brings in another force of its own towards the
“make-up” of the dog’s patterns of hair. When lying with his head
supported on his paws the lower part of his chest is closely applied to
the upper or flexor surface of the fore legs, and the long-continued
pressure of the latter against the downward or normal streams of hair
on the chest leads to its slope being reversed. This is shown in two
wide patterns of the whorl, feathering and crest, Fig. 40, resembling
closely the corresponding patterns on the chest of a horse. I had
the opportunity many years ago of examining in the Capitol Museum at
Rome two fine sculptures of Molossian hounds, when these matters of
hair-arrangement were occupying my attention, and was much struck with
the fidelity with which the ancient sculptor reproduced such small
facts as the reversed areas of hair in a dog. Phiz himself was not
more true to Nature in his delineation of the projecting hairs on the
human eyebrows. It should be added that the reversed hair in question
occupies only that part of the chest which is in contact with the fore
limb. If one cannot reckon any animal pedometers, to the credit of the
domestic dog I think one may fairly and metaphorically say that his
hairy coat gives an accurate mould of his habits.
CHAPTER XIII.
HABITS AND HAIR OF PRIMATES.
In spite of the satires of Swift we may not cavil at the natural pride
which has led man, Homo Sapiens, as he also calls himself, to confer
boldly on himself, and his lineal ancestors at any rate, the name of
Primates. This large and highest group of hair-clad mammals includes
broadly and somewhat loosely lemurs, monkeys, apes and man. The last
has not lost his hairy endowment, though it is sadly curtailed, and it
is well to remember that, except on the palms of the hands, the soles
of the feet and the terminal rows of phalanges of fingers and toes, man
_is_ a hair-clad mammal. Shakespeare calls him “paragon of animals,”
and Huxley “head of the sentient world,” and no reasonable person will
attempt to improve upon such pregnant tributes to his greatness. I
desire only to adhere that _quâ animal_ he is the best of all for my
humble purpose of historian of the chequered course of the mammalian
hair, better even than the domestic horse. His hair varies from a coat
so fine as to need a lens for the discovery of the separate hairs, to a
truly Simian profusion of thick and long hair such as that of the Ainu
or hairy aborigines of Japan.
Hair and Habits of Man.
The streams of his hair demonstrate two important facts about man:
first _what he has been_; secondly _what he has done_, that is to
say, his ancestry and habits of life, through an immense stretch of
time. These stories in hair are the culmination of a large number of
characters inherited and acquired, and their study in two selected
regions of lemurs, apes and man will be pursued in this chapter on the
lines which I laid down in Chapter VI. I have thought it well not to
give any connected account of the rest of his hairy covering so as to
concentrate attention on the two simplest and most striking regions.
The charts of his hair-streams and those of the lemur and ape have been
described with sufficient fulness elsewhere,[55] and no cartographer
has hitherto sought to improve upon them.
[55] _Direction of Hair in Animals and Man._
The back and the front surfaces of the trunk afford the two best and
most instructive fields of study, for the forces which act upon them
are of a simple kind, and may be traced upwards from the lemurs to man
as in the case of the forearms. The three drawings (Fig. 41) represent
the backs of a lemur, chimpanzee and man, most of the details of the
hair being omitted and their place taken by thick dark arrows which
show the line of the different hair-streams. This diagrammatic method
will make any misunderstanding of the main facts impossible.
The lemur has on the back of its neck a forward or headward slope
of hair and this passes on to the head itself, and on the back of
the trunk, as the arrows show, there is no departure from the normal
arrangement of the lower mammals. The lemur, therefore, requires
neither further description nor explanation.
The ape shows no material change in this region from the arrangement of
its lemur or monkey ancestor, in spite of the greater proportion of its
life which is spent in the upright posture; indeed, this is what one
would expect.
Hair of the Back of Man.
When the hair on the back of man is examined a remarkable change from
the patterns of any of his known or supposed ancestors is found. It is
by no means easy to trace the course of the hairs on the human back. A
young, hairy and dark-haired person gives much the best field, and a
lens may be necessary. In older subjects the hair is often so much worn
away by friction that the direction can no longer be followed. Suffice
it to say that the examination, though somewhat difficult, can well be
carried out if the proper conditions are observed; and that it bears
out the results which have come from the corresponding examination of
infants. _The arrangement is congenital._
From the neck the hair passes on each side nearly downwards, and in
the middle directly downwards in a narrow stream between the two
muscular borders of the vertebral furrows, and continues in this
normal direction to the end of the spinal region. It will be seen
that below the two upper arrows there are three levels of arrows, the
first with one, the second with two, and the third with one, on each
side of the surface of the back. At the level of the shoulder-joints
the side-streams curve upwards towards the spine and join the central
stream; at the second the direction is rather more upwards before it
curves inwards and downwards to the vertebral furrow; at the third the
streams curve slightly upwards and towards the middle-line and coalesce
with the other streams. The contrast between the straight, simple
slope of the hair on the lemur’s and ape’s back, and that of man is
very great. In the latter the side-streams make an angle of 45° or
less with the axis of the spine and _this arrangement is unique among
mammals_. It will be, therefore, necessary to inquire into its history
and causation, for it goes far towards reversing the well-established
and accredited pattern of apes, monkeys and lemurs. If the reader will
carry his mind back to the arrangement of hair on man’s forearm he will
see that it exhibits some features analogous to those on the back of
man. In the forearm there is that curious little stream on the extensor
surface which may be looked upon as a relic from the ape-stock, but
in the rest of that limb-segment man has boldly gone back, beyond the
ape, to an arrangement found in the lemur; and in the case of the back
of man there is the small primitive area down the vertebral furrow and
an entirely novel arrangement on each side such as might startle the
leaders of animal fashions in hair.
[Illustration: Fig. 41.--Arrangement of hair on the back of
lemur--chimpanzee--man.]
The question at once arises: “How has this change come to pass?” In the
case of the strange arrangement on man’s forearms I have shown that the
Pan-Selectionist thought he detected there one of his particular kinds
of vestige. He cannot find any such here. I can conceive a biologist
making play with Heredity, Variation and Selection in the case of an
ape, monkey, or lemur whose hairs are long and thick and functionally
very active. _There_ he might make use of the well-known “argument from
ignorance,” and maintain that we cannot be sure that such and such
factors might not have survival-value, but I defy the most hardy among
the Pan-Selectionist High Command to put in that plea in connection
with the fine short hairs of man which even require a lens for their
detection; they have little value as a protection of the skin from
friction; their arrangement has none. And if some leader did attempt
this task I doubt if the most docile Prussian would not rebel against
the statement that the withdrawal in question was “according to plan.”
My purpose, however, in this book being to build up and not to pull
down, I must perforce show a reasonable and better explanation of a
remarkable little fact.
Passive Habits.
The habits of man concerned in the _modus operandi_ of this change are
passive, and two in number; that of sitting with his back against some
supporting object, and of lying in sleep with his head more or less
raised on a pillow or its equivalent. In contrast with man, lemurs
and apes inhabit trees during their many hours of rest, and I doubt
if the number of hours thus spent by these and other wild animals
to that spent in active exercise is less than three to one, so that
their attitudes of rest would, if calculated to do so, contribute much
towards any change occurring in the patterns of hair. But, seeing
that the ape-fashion is similar to that of the lemur, and that this
normal arrangement is calculated only to be confirmed by the action of
gravity and the dripping of rain, and that they do not greatly indulge
themselves, if at all, in their equivalent for man’s armchairs, nothing
else would be expected in the hairy covering of their backs than what
we find.
The increasing tendency to the upright position in Eoanthropus Dawsoni
and Pithecanthropus Erectus to say nothing of the men of Cromagnon--led
man to use as supports for his back the walls of his rough caves which
he had adopted as dwellings instead of the branches of trees and the
nests of the ape. He no longer affected entirely those hardy habits
of sitting without support for his back that were _de rigueur_ in his
ancestors, who probably looked upon him with as much disapproval as
certain erect old ladies of the old school display towards the use of
easy chairs by the rising generation. Wearied with the struggle for
food, and against his savage rivals, he rested his back against the
sides of his rude abode. When he slept in this attitude the relaxation
of his voluntary muscles allowed mechanical forces to come into action
which tended to oppose the downward trend of the hair. We know from our
own experience that when sitting asleep with our backs supported there
always occurs a certain amount of sinking down of the trunk. In this
attitude are present, then, such conditions of the back and its hairy
covering as give rise to mechanical forces which would interfere with
the direction of the hair. These are, a heavy body, tending to slip
downwards slightly while resting against a fixed surface, a growing
tissue easily diverted from its normal course, and many hours spent in
the attitude in question.
The effects of these conditions increased with the increasing tendency
of developing man to attend to his bodily comfort.
But man spends also on the average at least a third of his whole
existence lying in sleep with his head on a pillow of some kind,
perhaps the skull of a _Felis Groeneveldtii_ in the case of
Pithecanthropus Erectus, and other such better objects, as he made more
study of the art of being comfortable. Those who know much of children
and sick persons and have watched them in sleep know that the habit
of lying on one or other side prevails largely over that of lying on
the back. The head being more or less raised by a pillow, the human
sleeper, even when lying on his back and more so when lying on his
side, is in a potentially and actually sliding position, a fact well
known to most persons from their own experience. It is easy to see
how such conditions are tending for a third of a man’s whole life to
reverse in some degree the direction of his hair and how they act as we
saw in the case of the sitting posture. But the very common _lateral_
position in sleep contributes its own peculiar share in pushing the
hair towards the spine, ceasing to do so only when the prominent
muscular border of the vertebral furrow is reached. I think it will
escape no careful observer of these simple facts of man’s resting life,
who also notes the remarkable course of the arrows on his back, that
the facts and their present explanation fit one another like a Chubb
lock and its key. The only alternative suggestion of the facts is that
some being with diabolic power has been at work and laying a trap for
poor human biologists in the 20th century A.D.
In confirmation of this process I would refer to an example which
agrees very closely with the above explanation. I knew an invalid
suffering from pleurisy and lung-disease who was much confined to bed,
spending much of his time propped high up on pillows. He had long dark
hair on his back and I was often struck, when examining him, with
the remarkable way in which the hairs were dragged upon so that they
pointed nearly in a vertical _upward_ direction. Here was a little
instance of an undesigned experiment in the dynamics of hair.
Hair of the Chest.
In the hair-streams on the chest of our chosen three, lemur, ape and
man, there are also some remarkable contrasts in the course they take.
Fig. 42 shows these in a vivid manner. Precisely as in the case of the
hair on the backs of lemurs, apes and man, we find on the chest of
those three types a normal direction on the two lower ancestors and an
entirely novel arrangement in man; the former, therefore, will need no
verbal description.
Man, the ever bold explorer and innovator has initiated on his chest,
as on his back, a fashion in hair unknown in any of the primates. He
is, in respect of his hair on these two regions, _sui generis_. On
the chest there is a critical area extending across the sternum at
the level of the second rib from a whorl which is found on each side
somewhat above the nipples. This is not less an ancient battle-field
than the Border which separated England and Scotland, and it has been
the site of its little conflicts, more especially _north_ of the
Border, corresponding to those of the wild days of Border warfare of
which Scottish history is full.
[Illustration: Fig. 42.--Arrangement of hair on the chest of
lemur--chimpanzee--man.]
At this level of the chest two streams of hair are _directly_ opposed
to one another. That which covers the chest below the dividing line
maintains in true old English style its conservative fashion and passes
downwards as in the ape and lemur. The more independent or Scottish
stream goes upwards on its way to the neck, the side streams passing
somewhat outwards towards the side of the neck, the central upwards and
inwards, converging gently on to the front of the neck. The arrows in
the figure show this very clearly. On the front of the neck the stream
pursues its upward way until it meets the downward flowing stream
from the lower jaw, and the _junction_ of these two streams lies over
the level of the upper border of the larynx in front, winding gently
outwards and upwards to the surface just below the lobes of the ears.
The opposition of the two streams in the neck is very familiar, as a
piece of practical experience, to those who shave, for it affords a
decided little resistance to the razor as it is drawn downwards, and
many persons change the position of the razor in consequence of it,
without troubling their heads with any scientific reason for the fact.
These are the facts of the distribution of hair on man’s chest, but
what is the interpretation? I would remark here that in my former
book[56] I gave what seemed to be then the best reason for it, but
further reflection on the matter has shown me that it was incorrect and
inadequate. I refer to this and one or two other corrections of earlier
views in a later chapter.
[56] _Direction of Hair_, pp. 88–93.
Interpretation of Records.
In discussing such a striking little fact as the one in question, an
illustration may serve as an introduction. From the glaciers of Mont
St. Gothard two great rivers take their rise. The eastern side of its
slopes gives rise to the Rhine, which flows in a northerly direction
to the Lake of Constance, the western to the Rhone, whence it pursues
a south-westerly course to the Lake of Geneva. No geographer would
doubt that certain physical features of the country were to be sought
in accounting for the contrary courses of two rivers arising from a
comparatively small region, and he finds it by a simple study of the
topography concerned. By similar methods we must ascertain why from our
little Mont St. Gothard at the level of the second rib, two streams of
hair separate and pursue nearly opposite directions.
A little knowledge of the superficial anatomy of the chest and neck
throws some light at once on the problem. It so happens that if one
made a simple map of these hair streams, and at the side of it a
drawing of the platysma myoides muscle, it could not fail to strike
one that the correspondence of the surfaces occupied by the two
phenomena was very significant. It is going too far to say that the
correspondence is complete, but it is so nearly so that one may fairly
say that the reversed stream of hair which begins at the second rib
and goes up the neck, lies over the platysma muscle. The stream of
hair does not extend up to the lower part of the face and lower jaw,
it does not cover the outlying portion of the platysma on the side of
the neck and it begins on the chest a little above the rather uncertain
origin of the platysma fibres from the fascia of the chest. But the
correspondence of its surface with the main part, or about five-sixths
of the platysma, is most suggestive.
This muscle is one of the subdermal sheets that are found in many
mammals, and though it is not a continuation or descendant of the
fly-shaker or panniculus carnosus, which is often referred to in these
pages, it is an analogous feature of man. It is _closely attached_
at its lower part to the skin over it and more loosely at its upper.
It has various functions attributed to it, as I will mention later;
but there is one effect of its action which is very evident in a thin
person, that is to say, it wrinkles the skin over it in a vertical
direction. This it does, whatever else it may do.
Struggles of the Platysma.
In interpreting this novel hair stream of man’s chest and neck we are
again brought into an atmosphere of struggle of forces. Something has
occurred in the course of man’s descent from the ape to interfere very
sharply with the course of the hair; and certainly if there be anything
in organisms that Heredity, Variation and Selection are unable to do
(even when adorned with capital letters, to make them, as Huxley said,
“like grenadiers with bearskins,” appear much finer fellows than they
are), it is to provide in this reversed stream of hair on man’s chest
some cunning “adaptation” to his needs. Selection will not serve; but I
think use and habit will. There can be little, if any, doubt that the
frequent and active contractions of the platysma muscle in the course
of man’s life are the efficient cause of the change of arrangement of
hair from a downward simian to an upward human slope. To this opinion
the anatomist will promptly reply: “Ah! I have thee there, friend
Lamarckian; are there not any number of apes and monkeys that also
have an active and efficient platysma?” Undoubtedly there are, and I
give here, through the kindness of Professor Keith, a short account
of that muscle in simiadæ. It is taken from an unpublished work of his
on _The Myology of the Catarrhini--a Study in Evolution_. The account
may be only interesting to the professed anatomist, but the conclusions
in the summary bear closely on the present problem. I give the exact
words from Chapter II., pp. 472, 479. The simian forms examined are
_semnopithecus_, _gorilla_, _chimpanzee_, _orang_, _gibbon_, _macacus_,
_cercopitheci_, _cynocephali_. “_Summary_: Every gradation is found
between the cynocephalic and human forms. The evolution lies in the
disappearance of the supra-trapezial origin and the superficial
labio-mental insertion. The opposite nuchal and mental angles of a
trapezoidal sheet are obliterated and a rhomboidal figure is left. The
change may be seen step by step through the _macaci_, _semnopitheci_,
_hylobates_, _troglodytes_ and the _orang_ to Man.
“The maxillary insertion in man is more extensive than the others, and
the insertion is more distinctly demarcated from the quadratus menti
origin. But slips between the two muscles are not uncommon.
“The sub-mental interdigitation occurs frequently in man, and although
its extent varies in the other Catarrhini it is always present.
“The upper nuchal fibres, being cut loose in the higher members of
the orthorachitial group from their primary origin, became aberrant
in their behaviour. Auriculo-labial slips, slips of union with the
zygomatici, or simulating a _risorius_, or a relapse to the primitive
medial dorsal origin and connection with the occipito-auricular muscles
may occur in man as in the others.
“Fasciculation of the muscle may occur in man and the _troglodytes_.
“That the functions of this muscle are indefinite is shown by the
numerous individual and generic variations. But that its presence is
essential may be judged by its persistence. It may depress the angle of
the mouth or the lower jaw, or help to flex the head upon the chest, or
help to empty the laryngeal air-sac if it be present. But as a matter
of fact all these functions are otherwise provided for. When tense it
protects the deep part of the neck somewhat, and it is usually active
in temper. The axillary part of the same sheet in the _cynomorphæ_
offers a similar puzzle as regards its functions.”
We have it thus on the highest authority that the platysma muscle is
active and persistent in a large series of monkeys, apes and man. But
the whole work has for its sub-title, “A Study in Evolution,” and
in the story of the platysma there is a picture of its progressive
development to that of man. There is evidence in the above account
of the muscle that a structure is found in monkeys and man which
might operate on the overlying streams of hair in any of these animal
forms--or might not--in accordance with the conception of struggle
between opposing forces which I have kept in view all through this
volume.
It is evident that in all animals below man the platysma has not
achieved any victory by its action over the streams of hair on the
chest and neck, and to my mind it is equally evident that in the case
of man it has carried through a very manifest “turning-movement.” It
will be objected, quite properly, that this is a matter of opinion,
and the pertinent question will be asked, “How do you account for the
absence of this reversed hair-pattern in apes and monkeys and its
absence in man, both having an efficient platysma muscle?”
The essence of a struggle is that it ends with the victory of one
adversary over the other, and as the race is not always to the swift
nor the battle to the strong, there is of necessity some uncertainty
as to the result of any struggle. The factors of time as well as of
overwhelming force are required for most of the victories of man over
man, and it is not less so in the victories of habit over ancestry in
the direction of hair, as I have repeatedly shown. The required time
is clearly at one’s disposal for this victory, and the “overwhelming
force” of habit and use is purely a question of the degree of
repetition and the efficiency of the contractions of the platysma, and
its greater use in man than in apes and monkeys. The uses to which it
was put in the lower forms not having been sufficiently overwhelming
for victory, no change in them has been shown. The cumulative effects
of the actions of a developing platysma in man, under the guiding
influence of his more complex habits of life, have turned the scale in
favour of the reinforced forces of habit, and the direction of the hair
becomes reversed nearly all over the area covering the muscle.
We must consider all the forces engaged in this struggle for mastery on
the neck and chest of man, and remember on one hand the power of the
normal slope of hair, the greater difficulty of altering the direction
of the thick long hairs of monkeys and apes, and their relatively
long resting hours; and on the other the shorter and finer hairs of
man and the increasing efficiency of his platysma muscle in varied
actions. Professor Keith mentions four functions of the platysma: that
of _depressing the angle of the mouth and lower jaw, helping to flex
the head upon the chest_, and to _empty the laryngeal air-sac_, and
_protecting the deep parts of the neck when it is tense_--adding the
significant comment that “it is usually active in temper”--I presume
this to mean bad temper!
Leaving out of account the emptying of the laryngeal air-sac, is it not
evident that the remaining three actions of the platysma are very much
more exerted in the case of man with all the numerous occupations and
movements of his head and neck, in obedience to his higher brain, than
in the apes, monkeys and lemurs, endowed with a fitful activity, with
fewer and less variable movements of their head, and long, long hours
spent in their particular form of meditation?
So, when the muscular sheet, which, as I have said, is _closely
attached to the skin of the chest and more loosely to that of the
neck_, contracts and becomes shortened between its origin on the
chest to its insertion in the face and jaw, it gives a most obvious
pull on the skin over it and wrinkles it vertically in a manner which
will strike any thin person who contracts it voluntarily before a
looking-glass. The connection shown between the action of the platysma
muscle and the change of hair is so close that it can hardly be
questioned that one is the cause of the other. If it be not proved to
demonstration it is “tremendously probable” and the connection falls
into line with the previous demonstrated cases.
I must add here a remark suggested by the views of man’s descent put
forward since this was written. The claim that man has changed the
direction of his hair on his back and chest by use and habit owing to
altered modes of life is not dependent on the simian theory of his
descent. The change to his present patterns on those two regions from
those of any “active arboreal pioneer” among insectivores is just as
striking and is open to the same line of explanation.
It would serve no useful purpose here to travel further over the varied
streams of hair on the body of man.
CHAPTER XIV.
MISCELLANEOUS EXAMPLES.
In this chapter a few of the rarer examples of hair-clad mammals which
present remarkable changes at critical areas of their hairy coats
may be considered with advantage. I have chosen six, of which three
appeared in my former book.
The Giraffe.
The two drawings of a giraffe, Figs. 43 and 44 were made for me for the
purpose of illustrating one of its habits and two of its peculiarities
of arrangement of its hair. This stately creature is the tallest known
animal and is the sole representative of its ancient family, more
common in the days when giants abounded. Its range is becoming more
limited and its enemies not less dangerous, and it is expected in the
course of some years to add to the number of the recently-extinct
creatures.
Habits.
Living mainly in dry sandy regions giraffes find their food exclusively
in leaves plucked from trees, and are said by some authorities to exist
for a long period without drinking, but an interesting account quoted
by Lydekker from Selous should be mentioned here. Selous writes that
on a certain occasion he reached camp “a little before sundown, just
in time to see three tall, graceful giraffes issue from the forest a
little distance beyond, and stalk across the intervening flat, swishing
their long tails to and fro, on their way down to the water. It is a
curious sight to watch these long-legged animals drinking, and one that
I have had several opportunities of enjoying. Though their necks are
long, they are not sufficiently so to enable them to reach the water
without straddling their legs wide apart. In doing this, they sometimes
place one foot in front, and the other as far back as possible, and
then by a series of little jerks widen the distance between the two,
until they succeed in getting their mouths down to the water; sometimes
they sprawl their legs out sideways in a similar manner.” Lydekker
adds that this position has to be assumed not only when drinking,
but likewise when the animal desires to pick up a leaf from the ground
or on the rare occasions when it grazes. This habit so graphically
described is the one which alone concerns my subject. The patterns of
hair peculiar to the giraffe need a short description.
[Illustration: Fig. 43.--Giraffe showing at A and B, hair-patterns of
a remarkable kind at the place where the main movements of the neck
occur.]
[Illustration: Fig. 44.--Giraffe in the act of drinking or browsing off
the ground.]
Hair Patterns.
Fig. 43 shows a whorl (B) at the side of the neck on a level with the
prominent spines of the seventh cervical and first dorsal vertebræ. It
lies exactly over a spot which may be well called a “critical area,”
for an important hinge of the whole mechanism of the giraffe’s great
neck is situated here. Though the remarkable length of its neck is
intimately associated with its daily needs for protection against
enemies and the supply of food from high-placed branches of trees, it
forms a real obstacle to the less important need of obtaining water
to drink or food from the ground as Selous and Lydekker show. The
protective value of the neck is picturesquely described by Mr. Beddard
when he speaks of it as the giraffe’s watch-tower, whence its keen
eyesight surveys the surrounding country for its enemies. But its
attitude in drinking, Fig. 44, gives a vivid idea of the play of forces
which takes place at the great hinge between the neck and the trunk,
and at this point the whorl has been produced on the skin in the course
of its laborious efforts to supply itself with water. The absence of
any other whorl or reversed hair on the whole of its neck and trunk is
most significant from the point of view of the dynamics of hair.
The second departure from the normal direction of hair is found on
the prominent portion of the spine, and it lies over this hinge-area.
In Fig. 44 is shown the mane proceeding along the whole of the neck
in the normal downward direction, and the arrows indicate the way in
which it becomes suddenly reversed at the critical point and the lowest
portion of the mane stands up and points upwards. This change is shown
by the two arrows whose points meet one another, and the facts of its
occurrence, here and nowhere else, at once suggest that the habit which
produced the whorl on the side of the neck has also contributed to the
change in the direction of the mane. The pattern here is precisely of
the same order as that of the cow’s neck which we saw to be caused by
its habit of browsing off the ground.
Bongo--Tragelaphus euryceros.
This West African antelope is a forest-dwelling species, about which
little is known as to its habit of life, though its form and anatomy
are well described by Lydekker. It has a powerful chest, long and
strong horns, and short hoofs, and it is shown in Fig. 45 with its
large pectoral whorl, feathering and crest, in which it strongly
resembles the domestic horse. One may be allowed here, as exact
knowledge is wanting, to point out that “reconstruction” of its habits
may be reasonably attempted along the lines laid down in these pages.
It is doubtful if any large mammal could possess so powerful a fore-end
with very muscular forelimbs, highly-developed pectoral patterns and
short strong hoofs without being a very fleet animal much accustomed to
relying upon its speed for its protection, and if a greater knowledge
of it be obtained in the future it is highly probable that this
prediction will be verified. Part of its habitat is described as the
Ashkankolu Mountains, a region where speed would be of great value.
[Illustration: Fig. 45.--Bongo. Showing on the strong muscular chest,
well-formed pectoral patterns.]
Kiang--Thibetan Wild Ass.
This member of the Equidæ is shown in Fig. 46 and there is an excellent
specimen of it at South Kensington. I have chosen it because it is very
unusual among others of its family in the possession of an inguinal
and axillary whorl, feathering and crest. No other than the domestic
horse that I have examined shows these patterns. They are nearly as
well developed as in the horse, and require no special description. It
lives in high altitudes up to fourteen thousand feet, and travels often
in large herds, its food being composed of the various woody plants
of these dry and barren regions. Lydekker says that it “is remarkable
for its fleetness and its capacity for getting over rough and stony
ground at a great pace.” From these facts one can gather that a large
portion of its working day would be spent in rapid locomotion from
place to place in search of its sparse food-supplies and in avoiding
enemies--two paramount objects of its existence which are pictured in
the two animal pedometers displayed on its hairy coat.
[Illustration: Fig. 46.--Kiang. Side view showing inguinal (W F C) and
axillary (W F C) patterns.]
Llama--L.
I refer here to the true llama or domesticated form of the genus Llama,
of which the vicunha and huanaco are the existing wild species. In the
stirring time when a handful of Spanish Conquistadores under Pizarro
conquered and trampled upon the ancient civilisation of the Incas this
useful animal was employed to an immense extent as a beast of burden.
Lydekker says that at the time of the Conquest of Peru it was estimated
that three hundred thousand llamas were employed in the mines of
Potosi alone. Prescott gives an excellent account of the use of this
animal in his _Conquest of Peru_. They were valued highly for their
strength and sureness of foot which were much needed in their long and
rugged journeys over the great passes of the Cordilleras, as well as
for the excellence of their flesh.
[Illustration: Fig. 47.--Fore foot of llama shown from behind (A) and
from side (B) with whorls of hair and reversed areas on each side.]
The only region of a llama’s body which is of interest in the present
inquiry is the fore-foot, figured in Fig. 47. It presents a very
remarkable arrangement of hair on its under surface, just above the
double hoof and spongy pad at the joint above the hoof. This is
found on each side towards the outer border of the hollow region,
and consists of a whorl from which the hairs radiate in a reversed
direction towards the upper part and transversely across the rest
of the hollow. Prescott speaks of “its spongy hoof, armed with a
claw or pointed talon to enable it to secure hold on the ice,” and
adds that “it never requires to be shod.” If one reflects upon the
ceaseless action during rough and slippery locomotion of this animal
throughout its working life on mountain passes, on rough stony paths
and ice-covered places, one can have no doubt of the reason why this
particular joint, so greatly used in maintaining a foothold, should
have acquired on this sheltered portion of its hair an animal pedometer.
The Parti-coloured Bear--Æluropus Melanoleucus.
This is a rare and peculiar form of the family of Ursidæ about which I
made a statement some years ago at the Zoological Society of London.
It is a “stocky” animal with a small head and broad short muzzle, a
feature to which it has no right according to its affinities. It is not
a member of the high-class Felidæ whose special prerogative it is to
wear their hair on a short broad muzzle in a _downward_ direction as
I showed in Chapter XI. Being a more _bourgeois_ creature than a cat
it has offended against such sumptuary laws as may exist in the animal
kingdom.
Its hair ought to be worn in the proper backward or upward slope such
as other bears, dogs and small carnivores display.
In my former note I modestly proposed an alternative suggestion to the
one I now offer, of this aberrant and strange bit of hair-country,
and this was that it was correlated with the broad short snout. As I
have remarked before this word “correlated” is used so loosely as to
mean almost anything the user likes, and it is, in my opinion, a fine
source of confusion of thought. Undoubtedly this shape of the muzzle
of the Parti-coloured Bear is linked somehow with the arrangement
of its hair on that region. But it is hardly to be imagined that
a direct reversal of hair from the proper bear-type, that is to say
from the mouth to the head, would be produced by the mere broadening
of the muzzle on account of some adaptation to its altering life. The
link surely is of a different nature, and analogous to that of the
corresponding surface in the lion and other cats, and that the cleaning
of its fur on the snout is done in feline and not in ursine fashion,
that is to say forwards, and that the breadth of muzzle is the reason
for the change of method.
Two-Toed Sloth--Cholæpus didactylus.
This weird creature is one of a decaying family whom naturalists, with
needless and frank brutality, called toothless. The term is neither
exact nor polite. It is very much as if one were to call a person
“toothless” whose front teeth had been knocked out, but whose remaining
teeth were good and useful. But it represents so important a taxonomic
character that one must allow for what seems bad manners on the part
of zoological leaders who are, as a rule, full of the milk of human
kindness, and seldom in these days quarrel even among themselves,
adopting the motto _nihil animalium alienum a me puto_.
[Illustration: Fig. 48.--Two-toed sloth, showing action of gravity upon
the long thick hairs.]
The sloths form an excellent example of the action of gravity upon long
thick hairs, and the Fig. 48 given will explain this. They are New
World animals, though indeed they have what we call an “Old World”
look, and are truly ancient. They spend the larger part of their
time upside down in the manner represented in the drawings. They are
arboreal and nocturnal animals that come down to earth in search of
food when things are quieter below, and will wander for considerable
distances, walking slowly on the outer borders of their feet and the
feet turned in.
These being the few facts of their lives which concern the present
subject one comes, as usual, to interpretation. These tree-sloths are
descended from an older form that inhabited the ground, so that the
present mode of life, which is so largely arboreal, has been acquired
by dint of long years of struggle and adaptation to bitter needs.
It seems hardly reasonable to call in the aid of selection for the
production of its singular disposition of hair though that factor ruled
in the production of its arboreal habit. It is almost flying in the
face of common sense to attribute this upward, or downward (according
to one’s point of view) singular arrangement to anything but the
effects of gravity upon its long hairs. If it be not so, it looks a
remarkable likely solution of this small problem.
CHAPTER XV.
EXPERIMENTAL.
About ten years ago I began an investigation into the results of the
application by man to the domestic horse of various forms of harness,
desiring to find out if these results were capable of being transmitted
from one generation to another. In 1908 I had not got very far, but
thought it well to bring before the Zoological Society of London the
results observed up to that time and read a paper entitled, “Some
observations on the effects of Pressure upon the Direction of Hair
in Mammals.” It was kindly received, but was not published in their
proceedings, as it appeared to the Publication Committee a paper more
suited to “another place,” presumably those of a veterinary society.
It was illustrated by the two figures I give here of a horse in full
harness, and another with the chief results as to changes of the
direction of hair, or new patterns, displayed on its coat.
Progress of Inquiry.
Being disposed to think that the investigation could be carried
further, I proceeded to look about for any examples in horses which
might show the transmission of these artificial results to their
descendants, and had to wait awhile before I could see which of the
regions affected by the pressure of harness were likely to afford the
required phenomena. These were in due time forthcoming, and will form
the chief subject of the present chapter. I look upon them as cases of
an _undesigned experiment_ and will describe them later.
In the present stage of science all hypotheses must be submitted to
the test of experiment before they can enter the charmed circle of
natural laws. For this reason one must endeavour to apply the test of
experiment to the hypothesis before us.
The Nature of Experiment.
Hitherto I have gone no further than the region of experience and
observation, from which, Jevons says, “all knowledge proceeds.” There
has been abundance of observation of phenomena in this quest and I
have ventured even on hypothesis. Experiment is shortly defined by
Jevons as _observation plus alteration of conditions_. He points out
that when we make an experiment we more or less influence the events
which we observe, as when we bring together certain substances under
various conditions of temperature, pressure, electric disturbance or
chemical action and so on, and then record the changes observed; and,
that experiment may be of two kinds, experiments of simple fact and
experiments of quantity. It is unnecessary here to describe all the
rigorous rules that the man of science so rightly imposes upon himself
before he claims to have proved his hypothesis, merely adding that
among others he requires, Exclusion of Indifferent Circumstances,
Simplification of Experiments, Removal of Usual Conditions,
Removal of Interference of Unsuspected Conditions, Blind or Test
Experiments, Negative Results of Experiment, and he lays down the
limits of experiment. Those who have not for themselves investigated
some scientific problem may learn from this statement some of the
difficulties of the work of scientific men and will not fail to respect
and admire the caution, patience and honesty of the scientific worker,
and will perhaps feel the more gratitude to a class of men by whose
self-denying labours they live and move and have their being in a
modern state, and by whose discoveries, thus established, they are
frequently preserved from premature death.
Experiments for the Present Purpose.
Now in the matter of experiment for the proof of the thesis that
changes in the habits of an animal _cause_ the changes observed in
their hair, it is at once seen that, _ex hypothesi_, no one can impose
and work with such calculated conditions as are ordained by experiment,
strictly so-called. The action of a habit is a slow process and the
movement of a hair is slow; moreover the lifetime of a man is too short
and that of a horse, for example, too long to allow of any individual
experimenter applying artificial pressure through many generations of
horses, so as to be able to verify his assertion that the effects of
artificial pressure do what is claimed, and that these effects are
transmitted from one generation of horses to another. One can conceive
a calculated experiment of the kind made with numerous individual rats,
and successive generations, but it is hardly likely that effectual
pressure could be applied to the hairy coats of such small and elusive
mammals as would serve to test the hypothesis.
Undesigned Experiments.
We are thrown back, then, on such experiments as may be provided
for us by the uncalculated operations of man through many ages.
This class I call undesigned experiments and have had more to say
about numerous examples of these in another place.[57] Using the
term experiment broadly we see many occurrences which consist in an
accidental observation of a fact, and Jevons mentions five of these
which have led to organised results in science--the double refraction
in Iceland spar by Erasmus Bartholinus, the twitching of a frog’s leg
under stimuli by Galvani, the light reflected from distant windows
with a double-refracting substance by Malus, the form of a vertebra
by Oken, and the peculiar appearance of a solution of quinine by Sir
John Herschel. But he notes something further than this, that is,
the way in which astronomers make the earth’s orbit the basis of a
well-arranged _natural experiment_. He says further that “Nature has
made no experiment at all for us within historical times” among animals
living in a state of nature, allowing at the same time that man has
made an approach to experiment in his domestication of many animals.
Huxley himself kept an open mind until the last as to the validity of
Natural Selection in the Origin of Species, because of the fact that
races which are sterile together have not yet been produced by human
cultivation, for example, the sterility of mules, the human product of
the jackass and the mare. I allude to this to show that such a result,
if effected, would have constituted a valuable experiment in biology in
favour of Natural Selection.
[57] _Contemporary Review_, June 1917.
Harness on Horses.
Man has, however, been carrying on unconsciously throughout a great
stretch of time an experiment upon the hair on the coat of a horse
by the use of harness. This is an old story and its rudiments are
mentioned by Professor Scott Elliott.[58] He states that the men of
Cromagnon are believed by a high authority as to their rock-paintings
to have depicted some marks which represent rude harness of some kind,
though he himself expresses doubt on the matter. He also quotes the
same authority for the figures made by the Madelenians as having found
signs which can be interpreted as halters or even bridles. Be this as
it may, we need not carry our search for the use of harness to this
hoary antiquity, but know well from history that for many thousands
of years man has been employing harness on his friend and servant,
thus making the essential conditions for an experiment of which he and
his servant were alike unconscious, that is to say, he influenced a
growing living structure, the horse’s hair, by the artificial force of
pressure, applied to the coat at various points. These varied from age
to age as to fashion and material, and the present full development of
harness of a draught horse was probably slow in coming.
[58] _Prehistoric Man and His Story._ G. F. Scott Elliott, 1916,
pp. 169, 206.
Examples of the Effects of Pressure.
Looking at the figures of a horse harnessed, and another without
harness, Figs. 49 and 50, one sees on the latter eight different
regions where patterns of hair, not found in the horse normally, are
displayed. They are as follows:--
A. The under surface of the neck. Pattern due to the collar.
B. The hamstring region. Pattern due to the kicking
strap.
C. The hollow corresponding to Pattern due to strap of
what we should call the saddle.
armpit.
D. The coccygeal or tail-region. Pattern due to the crupper.
E. The side of the neck. Pattern due to the reins.
F. The shoulder. Pattern due to the shaft.
G. The side of the face. Pattern due to strap of
head stall.
H. The border of the neck _under_ Pattern due to collar.
the collar.
All these aberrations from the normal are rare except the first
(A), and all are based on the observation and drawing of individual
specimens which I brought before the Zoological Society and the details
of which are given in a note on page 129. The rarer seven examples are
described because taken together they show what the pressure of harness
_can_ do at certain points where its pressure is adequate, and they
are all situated where they might be expected if such a force could
effect hair-changes, and there are _none of them found on areas where
neither pressure nor underlying muscular traction_ can act efficiently.
Thus in many thousands of horses I have never seen a hair-pattern on
the middle of the flank or the under surface of the abdomen or the
middle of the back or gluteal region or on the fore or hind legs. This
negative evidence is of great importance, and must be taken for what it
is worth. I may venture to remind the reader that every one of these
phenomena is an artificial product of man’s treatment of the horse.
They come thus under the category of undesigned experiments.
The only one of the eight artificial patterns, which as a rule are in
the form of a whorl feathering and crest, that needs, further close
attention is the pattern A, produced on the under surface of the
horse’s neck by the collar, and this will be examined separately.
[Illustration: Fig. 49.--Domestic horse, fully harnessed.]
The Selected Example--Ventral Surface of Horse’s Neck.
If I set out to convince a doubting opponent that these things are
as I assert, three conditions may at once be laid down. First, it
must be shown that the patterns found here are not part of a normal
arrangement. Second, that they are produced by pressure of the harness.
Third, that examples of them be forthcoming in young horses never
exposed to the action of harness.
[Illustration: Fig. 50.--Side view of domestic horse, showing eight
areas of reversed hair, A, B, C, D, E, F, G, H, all of which were
situated under portions of the harness.
B. Pattern on hamstring region, under the breeching.
Examined 24th December, 1907. Roan hackney, recently clipped,
showed on the offside on the hamstring region, a reversed area
of hair proceeding vertically upwards and ending in a crest, in
the position where the breeching rubs during locomotion. Thirteen
cases examined, other twelve similar.
C. Pattern on lower axillary region, under belly-band.
Examined 4th March, 1907. Small grey hackney with reversed area of
hair in lower axillary region, with also a crest nearly horizontal
lying along upper part of this area under the belly-band. Eight
cases examined, the other seven similar.
D. Pattern on tail region.
Examined 29th November, 1907. Bay hackney, on each side of base of
tail where the crupper rubs during locomotion, is a wide reversed
area of hair five to six inches long, in which the hairs were
arranged at a right angle with the axis of the spine on the upper
border and feathering out on the lower border into the general
stream of hair. Three cases examined, two others similar.
E. Pattern on side of neck under the position of the reins.
Examined 21st December, 1907. Small mouse-coloured hackney recently
clipped. On the offside of the neck where the reins rubbed against
the neck there was a wide reversed area of hair with a well-marked
crest in front. Five cases in all examined, the four others
similar.
F. Pattern on shoulder.
Examined 15th September, 1905. Bay cart-horse, reversed area lying
nearly horizontal under the shaft of the cart; hairs formed into a
whorl, feathering and crest lying posteriorly--pattern four inches
in length, on near side only. One case only examined.
G. Pattern on side of face.
Examined 25th May, 1905. Grey hackney with wide reversed area of
hair along side of face ending above in oblique crest, under a
strap of the headstall, on the offside only. Two cases examined,
the other similar.
H. Pattern on border of the neck under the collar.
Examined 28th September, 1906. Bay cart-horse. On near side under
the collar which was lifted up while the horse was resting, the
hairs at the border of the neck were formed into a large whorl.
One case only examined.]
_First._ The normal arrangement of hair on the under surface of the
horse’s neck shows an even stream passing from the head to the chest,
where it is interrupted by the pectoral patterns, and during that
course resembles precisely the other normal streams in this and other
mammals.
The opponent asks, “How do you know this is the normal slope, and
that the patterns you describe are not normal, and what you describe
as normal is not a variation?” This is a perfectly proper and timely
question and can only be answered fully by examination of and noting a
large number of draught horses.
The Normal Arrangement on the Ventral Surface of the Horse’s Neck.
This examination has been made in a number of specimens large enough
to satisfy the most exacting opponent. In all, 748 were examined
as to the hair on the under surface of the neck and 338 of these
presented the normal arrangement and 411 showed patterns of various
kinds ranging from a trifling reversed area two to three inches long
on one side of the middle line, to a finely-formed whorl, feathering
and crest occupying the whole of the surface where the collar is able
to reach. These two limits are shown side by side in the figures. I
should add that among the 411 which I term abnormal, for the sake of
clear contrast, the number of varieties of pattern were numerous and
bewildering.
Cart Horses.
A very significant result followed from a special examination of
300 cart horses, as distinguished from hackneys. These showed the
astonishing number of 277 specimens of what I call the abnormal and
only 23 of the normal type. This special group in no way weakens the
force of the larger study of 748, for the 300 cart horses are included
in it, and, if removed, would have left the normal specimens in the
hackney or general group very much more numerous. Looking at the cart
horses, which are specimens of a highly-specialised breed for heavy
draught purposes, one may assert with some confidence that, _for them_,
the normal pattern of the hackney is becoming their abnormal. It must
be remembered that these great creatures with large muscular necks are
during most of their time of work pulling hard against the collar,
and the very conditions required for making patterns of hair through
pressure of harness are present in a remarkable degree. It is indeed an
_undesigned experiment within an experiment_.
Analogy.
In addition to these statistics which may be taken as conclusive on
this question of the normal arrangement, I must point out that it is
against all reason, and analogy from _all other_ mammals, to doubt that
the normal arrangement is as I describe it. No hair-clad mammal either
within the family of the Equidæ, or without, has any other arrangement
on the under surface of its neck than what is here shown to be the
normal one--a uniform uninterrupted slope from the head to the chest.
There is also a feature of this greatly variegated piece of the horse’s
coat under its neck, and that is that it is so highly variegated
with diversity of pattern as to make it unlike any normal or natural
structure or character in any animal. _That_ is not the way Nature does
her normal work. It would be impossible to give illustrations of many
of the patterns here found, though I have notes and sketches of a large
number taken from the examination of thousands of specimens; so I have
selected eight (Figs. 51, 52, 53, 54, 55, 56, 57 and 58) of the best
representatives of these and the details of each are given under each
figure.
Effects of Pressure by Harness.
_Second._--The next stage of the inquiry demands that one should show
the patterns to be due to pressure.
[Illustration: Fig. 51.--Roan cart horse, examined 25th September,
1914. On left side of middle line of the under surface of the neck a
short reversed area three inches long, lying vertically--none on the
right side.]
[Illustration: Fig. 52.--Grey cart horse examined 25th September,
1914. Long central feathering (F) proceeding vertically upwards in
middle line of neck from whorl (W) and ending in a crest (C) at the
upper limit of region, through which the collar can move in active
locomotion.]
In the accompanying drawings the under surface of the neck and the
chest of each horse is shown with the collar in place, the centre
portion of which is cut out so as to show the arrangement of hair
beneath, and some of the varieties are seen to extend for several
inches above it. In considering this process one ought to watch the way
in which the collar of a horse, as a rule, is seen to move up and down
as he trots, for in most cases, except in cart-horses, the collar fits
very loosely and is easily jolted upwards. This will explain why the
patterns often extend upwards above the proper position of the collar,
but it must also be remembered that _never_ have I found a pattern
higher up in the middle of the neck than a loose collar can reach when
jolted. (Close to the lower jaw there is a whorl or pattern often found
which belongs to a different category, and is not to be confused with
the patterns in question.)
[Illustration: Fig. 53.--Brown hackney, examined 9th October, 1914.
Small reversed area of hair lying under collar in middle line of under
surface of neck, passing vertically upwards three inches long, in
central position.]
[Illustration: Fig. 54.--Brown cart horse, examined 25th October, 1914.
Whorl, feathering and crest (W F C) in middle line of under surface of
neck, beginning below where the collar should lie in usual position.]
In the conditions described there is present exactly that frequent
pressure of a moving body against the growing hair, which is requisite
to produce changes in its direction, as well as the more fixed pressure
of the collar when it is fitting firmly against the lower part of the
neck.
By way of confirmation of the view that this is the _modus operandi_
one has only to point to the other seven regions shown in Figs. 49 and
50, in which the connection between the pressure of harness and the
production of a new pattern is beyond all doubt one of cause and effect.
[Illustration: Fig. 55.--Brown cart horse, examined 25th October, 1914.
Whorl, feathering and crest (W F C) in middle line of under surface of
neck beginning underneath collar and proceeding vertically upwards for
six inches.]
[Illustration: Fig. 56.--Bright bay pony, examined 29th October, 1914.
Very muscular neck. On under surface on each side a wide curving stream
of hair passing towards middle line and joining in a central upward
stream ending above in a tuft (T).]
The Proof of Transmission of Pattern.
_Third._--To show that the effects produced by pressure in one
generation are sometimes inherited by its descendants it is necessary
to examine a few examples of young horses who have never borne the yoke
as yet.
[Illustration: Fig. 57.--Brown hackney, examined 29th October, 1914.
On under surface of neck beneath the lowest portion of an ill-fitting
collar, a wide area of reversed hair on each side coalescing in a
central upward stream.]
[Illustration: Fig. 58.--Brown hackney engaged in drawing a low Swiss
cart, with loose collar low on neck. Examined at the Croix in Jura
mountains, 24th September, 1912. On lower surface of neck under the
collar three reversed areas observed; one central (F), two (W, C)
central and similar; all three showing a whorl, feathering and crest:
central area placed vertically, lateral ones slightly oblique. _A very
rare condition._]
I examined some mares of the farm-horse type with their foals in a
field at Radley in 1915 with the following results. All the mothers
showed the common reversed area or pattern on the under surfaces of
their necks. Of the five foals all but one showed clear evidence, even
in their thick young coats, of a similar pattern, the fifth had none.
I also noted two similar examples in a field at Harrogate in the same
year and both the mothers and the foals showed the usual pattern;
and again at Radley in 1918 four more foals, one of them 24 hours
old, who all showed this reversed area. Here then are ten examples
of undoubted transmission of the effects of pressure by harness in
subjects so young as to be still suckled by their dams, and, of course,
never themselves touched by such pressure. I submit that even one such
unmistakable example would be enough to prove the case, and that the
necessary conditions of a rigorous undesigned experiment by man have
been fulfilled.
Objections.
At the end of this chapter which concludes the facts of the case I
think it may serve to make the position a little clearer if I state
objections which have been or might be raised.
It will not escape the mind of any person who has followed critically
this process of inquiry, that in Chapter VII, where the immense variety
of the patterns found on the side of the horse’s neck are described,
there is an apparent resemblance between them and those on the ventral
or under surface of the neck. The former were shown to be due to
natural forces, those of sustained and repeated underlying muscular
traction of muscles and jolting of the neck in locomotion; whereas
in this chapter a considerable number of patterns have been brought
forward and pictured on the under surface, and these are attributed to
artificial pressure from harness. The reasonable objection is raised,
“Why should the former be considered natural and the latter artificial
in their origin?”
The answer to this is supplied by a consideration of the muscles shown
in the two contrasted regions. In Figs. 3, 4 and 5, the muscles of the
side of the neck are shown to be remarkably _strong and numerous_ (in
three layers), and _diverging in their directions_. In the muscles of
the under surface of the neck of the horse, see Fig. 12, the muscles
of the two sides shown are nearly parallel and no conflict of opposing
or diverging muscles can well take place in this “debateable land.”
If there were much divergent or opposing action going on it would, of
course, produce the effects on the hair towards the _upper_ part of the
neck, where the muscles tend to diverge more and more as they pass to
the head, and I have stated above that not a single instance in many
thousands of horses has been found above the level where a loose collar
ceases to rub when jolted upwards. This is very conclusive on the
matter of diverging or opposing muscular action.
Then again the jolting in locomotion, which, in the case of the side of
the neck is probably more effectual in producing changes of hair than
even muscular traction, is almost absent from the under surfaces, as
can be learned from careful watching of the motion of a horse.
Another reason which meets this objection very fully is that I have
shown that 300 cart horses presented 277 of their number with reversed
areas of patterns in the middle line of the under surface of the neck
and these thick-necked animals are just those in which the collar is
closely applied to the front of the neck in their heavy draught work,
thus rubbing almost incessantly against the lie of the hair. In the
thinner necks of the hackneys there are comparatively few indeed of the
patterns found here and their collars as a rule fit very loosely and
badly, and these frequently show a jolting up and down _clear of the
neck_, which is seldom if ever present in a well-formed cart horse.
Further proof of this is shown by the simple fact that it is _under the
collar and within its range of movement_ that the changes of hair are
produced.
No artificial pressure such as that of a collar is exerted on the
parts of the side of the neck where the patterns are found; so I would
submit that these two selected and much-disturbed areas owe their
hair-patterns to two wholly different forms of mechanical cause.
I referred in the Preface to an important criticism of my earlier book
on _The Direction of Hair in Animals and Man_, and will now treat this
in some degree of detail. It is from the pen of an eminent American
biologist, then Miss Inez L. Whipple,[59] now Mrs. Wilder Harris, and
it is a careful, independent and thoughtful contribution from one who
by her studies in this field and in the study of the mammalian palm and
sole is widely known, and as widely respected.
[59] _Science_, 23rd September, 1904. New York.
Miss Whipple refers on page 403 to certain whorls and featherings on
the backs of the lion, ox, giraffe and larger antelopes, which I then
attributed to the action of the _panniculus carnosus_ in shaking off
flies. I am free to confess that the action then invoked by me was
inadequate and incorrect and the explanations now given of them in
Chapters X. and XI. on the ox and the lion, I think, are less open to
criticism.
Again on page 404 she mentions the view formerly expressed as to the
cause of the reversal of hair on the chest of man. This, also, I have
reconsidered fully in Chapter XIII. where the action of the platysma
muscle is held to be the cause of that remarkable reversal.
On page 403 the mistake I made in calling the reversed area over the
ischial tuberosity of the ischium in a dog a whorl is pointed out. This
is corrected in Chapter VI. on the Dogs.
These three are the only errors of any importance that I acknowledge
at once. A certain number of minor points are questioned in the
Review, and the theoretical portion is strongly criticised. It would
be irrelevant to the main purpose of a book which is limited to the
subject of Habit and Hair Direction in Animals to introduce some of
the more debateable branches of the subject of the former book, such
as tufts, the direction of the hair on the mole, the classification of
the hair-streams of the mammalian body into primitive, those modified
by morphological change, and those due to use and habit. This last is a
very wide subject and is far beyond the present limits.
I freely make another acknowledgment. The whole of the subject of the
Direction of Hair in Animals and Man was taken up _ad hoc_, that is to
say, for the purpose of testing the unpopular doctrine of Lamarckism.
If this be an offence against the highest spirit of science, I can but
accept the charge with a sigh, and go on, “faint yet pursuing.” There
is consolation in finding that increased study of a subject is bringing
order out of chaos, even if the field be small and the immediate crop
poor.
The following are some of the objections raised to the theoretical part
of the book:--
The most serious charge against my interpretation of the mode of
formation of patterns (whorls and tufts) is that there is a lack of
harmony between my preliminary statement that whorls are due to motor
or muscular causes and a subsequent explanation of some of them as
due to external pressure. I did not state then as clearly as I do now
in many passages in the present chapters that for pattern production
there may be at least four causes: _friction_, _pressure_, _gravity_,
_underlying muscular traction_, and that whorls and featherings may,
of course, arise from some other external force acting on the hair
at the decisive point of struggle, just as well as from the more
common cause--muscular traction on the skin. I think in this region
of the Review and where she deals with Selection, she shows signs of
that scientific monism which is still affecting many of our great
biologists, that is to say, they desire a world-empire in evolution
for the great factor of Selection, and will stretch their arguments
considerably to save its face. This is shown in the Review on page 406
where a very thin plea is put in on behalf of adaptation and Selection
in regard to hair-directions, as in man’s minute hairs, which cannot be
seriously maintained. That earth is stopped!
Darwin’s open-minded dualism in this matter of the factors of evolution
appeals to me at any rate more than the jealous attitude of Weismann
and his eminent adherents.
Miss Whipple is less determined than I am in claiming for Selection
the cause of the primitive slope of hair in mammals. It is the only
conceivable arrangement that could exist for the advantage of the
primitive forms in their simple life, and is, I submit, as much a
matter of adaptation to needs governed by Selection as the possession
of a dermal covering itself.
One more point, which, I think, is a small one and a fair one to raise,
is worthy of a few remarks. Miss Whipple states that before variations
in hair-direction can be logically attributed to external forces
(giving the instance of the human scalp) “it should be shown that a
change in the direction of the external, more or less wiry portion
of the hair produces a change in the direction of the follicle.” As
it happens, this change is easily seen in the case of the reversed
hairs of the human forearm, if the hair be dark and the skin thin.
The essence of the theory that dragging on the skin by muscular
traction causes the hair to change its direction is that the relatively
important portion within the hair-pit is pulled here or there according
to the incidence of the prevailing force. But it is, to my mind, very
clear that much repeated friction or pressure or gravity acting on the
external and longer portion of the hair must, in course of time, drag
the portion buried in the skin with it and so change its direction.
These two portions of a hair cannot be arbitrarily separated. Shortly,
one may say that the push of a force is as evident as the pull. A
similar change in the direction of the buried part of a tree-trunk from
a prevailing wind can be traced.
The last point is that I “omit to explain the mechanical process by
which divergent muscular action could affect hair-direction.” This is
well answered in the chapter on “Can muscular action in the individual
change the direction of the hair?” for there it is shown by numerous
examples in the human eyebrow that the muscles underneath the hairs
which are embedded in the true skin for a tangible depth, _do_ play
havoc with the normal arrangement of hair, as the conflict proceeds,
the resultant “pull” being actually engraved, signed and sealed by
physiological wrinkles of the forehead and face.
CHAPTER XVI.
FIRST SUMMARY.
A large body of facts and an adequate proportion of reasoning have been
brought together in the preceding chapters. As far as I understand the
proceedings in a court of law, the business of arriving at results or,
as they are there called, verdicts, consists in collecting as many as
possible of the facts which bear on the case, these are sifted and
verified, or the reverse, a certain reasoning on them is carried on;
on this the verdict rests. This case before the court is of a civil,
not a criminal nature, and it is a claim made to a certain _derelict
property_, that is to say, the honour of forming patterns on the
hair of animals, claimed by Use and Habit. The facts concerned have
never been disputed, possibly because they were not thought worth the
trouble, but they have the singular merit of being open to almost any
educated person for confirmation or correction, and the reasoning is
certainly not profound, though I think it is cogent. In seeking a
result in such a cause, or verdict, one claimant might content himself
with an arrest of judgment, another that judgment should go by default,
and a third would claim proof. It is with the last I desire to stand.
_In one word the claim is that of causation._
Now no one can deny that between the groups of phenomena, habits and
hair-patterns there is an evident relation; but the question may still
arise, “What is the link between them?” I have just said that the facts
are unquestioned; substantially they are unquestionable, and they are
open to the charge that they belong to the dust-heaps of science, that
they are, biologically speaking, such as used to engage the attention
of Nicodemus Boffin. Perhaps they are. Of course if they were just
collected haphazard and treated like a big collection of little shells
in a cabinet, without reference to their natural order, they would
possess no evidential value even if they were pretty, for so long as
a natural fact remains without its suited interpretation, so long it
belongs not to science. Hear Jevons: “Whatever is, is, and no natural
fact is unworthy of study for the purpose of its interpretation.”[60]
Hear also Sir E. Ray Lankester: “That only is entitled to the name
of science which can be described as knowledge of causes or knowledge
of the order of Nature.”[61] Fortified by the authority of a great
logician and a great biologist I proceed to claim proof of causation.
The stages of the case may be summed up as follows:
1. It has been shown that during the lifetime of an individual,
muscular action can change the direction of the hair. Chapter VIII.
2. Undesigned experiment has shown that changes in the direction of
the hair, mechanically produced in the individual, are sometimes
transmitted to the descendants. Chapter XV.
3. In all the selected examples adequate and ascertainable causes
have been demonstrated.
4. The changes of hair described, with hardly an exception,
cannot be conceived as resulting from the factors of organic
evolution--heredity, variation, adaptation and selection--indeed no
serious attempt has been made to connect them in any way with utility.
[60] Jevons, _Principles of Science_, p. 269.
[61] E. Ray Lankester. _Advancement of Science_, p. 7.
Causation.
For my sins, the most obvious of which is that I made an unfortunate
choice of my first birthday, I had to learn up the dreary pages of
Mill’s _Logic_ and those of other philosophers, for the pleasure of
taking a medical degree, and was reduced to that orthodox state of
mind in which one was forbidden to suppose that, in the world around
where common men and women, every day and all day, are tracing causes
for the occurrences they see on every hand, there was anything at work
which could be truly called a cause. It was but natural to fall into
the nihilism of the Mill and Karl Pearson school. Having neither the
knowledge nor the hardihood to discern that their bewildering notions
of causation could be gainsaid, I had to remain submissive and as
much contented as possible with their views of an elusive subject.
This state of passive resistance was not relieved until I had the
great advantage of reading a valuable book by the late Dr. Mercier
on Causation, which seems to have let some fresh air into the musty
doctrines of the orthodox and autocratic philosophers. No one who has
read this work can doubt that after all there is such a process as
causation, and that to find a cause for events is not merely a pursuit
of the vulgar, but a duty of scientific persons.
Mill appears to have given eighteen different accounts of causation
and to have contradicted himself over and over again in his works
dealing with this puzzle, devised mainly by Hume and himself; and his
successors, such as Dr. Mc’Taggart, the Hon. Bertrand Russell of “Dog
Fight” fame, Mr. Welton and Prof. Karl Pearson, have only got as far
as to reduce the number of his definitions and put his views into more
modern, but equally misleading terms. Without any disparagement of
their other claims to respect and admiration, one may venture to throw
overboard this school of philosophers when considering causation, and
one may walk and talk in a clearer atmosphere.
The subjects here considered are cause, effect, result, reason,
evidence and proof, and all can be seen to enter into my small thesis.
They may then be defined, according to Dr. Mercier, as follows:--
1. A cause is an action, or cessation of action, connected with a
sequent change or accompanying unchange, in the thing acted on, or
more shortly for my purpose _a cause is an action upon a thing_.
2. An effect is a change connected with a preceding action.
3. In reference to causation a reason means the cause of an unchange.
4. A result is the changed state that is left when an effect has been
produced.
5. Evidence is of three kinds: evidence of sense, evidence of reason
and evidence of hearsay.
6. Proof is evidence inconsistent with an alternative to the
assertion.
I turn now to the aid given to the case before the jury, and must show
how Dr. Mercier’s definitions establish it.
The cause of the changes described is the action of certain new habits
on a living growing structure of the mammalian body.
The effect is the change connected with the preceding change of habit.
The result is the changed direction of hair, in other words, new
patterns, left when the new habits have been produced, and have been
long enough in operation.
The reason for the unchanges observed in many instances is the
primitive force of the normal direction of growth of the hair.
The proof of the thesis is that the changes described in the hair--the
evidence--is inconsistent with an alternative assertion.
To Some Critics.
It may save time and trouble if replies are given in anticipation
to certain classes of critics. I refer of course to those who are
well-informed in their branch of knowledge.
To those of high authority and learning, those who ride on white asses
and that sit in judgment, who may seek to throw the case into chancery,
saying, “This will never do, it contradicts current biological
opinion.” I can only meekly reply that current or orthodox opinion
is frequently wrong, or (shall I say) seldom right, and that the
history of human thought is strewn with examples which may justify my
impertinent reply.
To another who says, “I daresay you are right in your claim, but there
are too many metaphors,” I would suggest that, so long as metaphors are
not used as arguments, the more metaphors--within limits--the clearer
the meaning of the statement.
To him who grudgingly allows, “I think you have proved your case--but
what does it prove?” I reply that it proves what it set out to prove,
no more and no less, and it is an integral part of proof of a larger
claim. And if he further grumble that these matters have no interest
for him, one may ask him to live and let live. “What have I now done in
comparison of you, is not the gleaning of your grapes of great Ephraim
better than the vintage of this little Abiezer?”
To the man who reads the preface and the headings of the chapters,
glances at the illustrations, detects one split infinitive, two
misspellings and three errors of punctuation, goes home to tea and
writes his opinion--it may suffice to remind him of “that curious
mental state which looks past problems without seeing them.”
I will conclude this section with a parable.
In the year 1788 Arthur Young in his travels through France visited the
desolate region of the Landes. “Wastes, wastes, wastes!” was his lament
over neglected Brittany, and no less could he say of the Landes, at
that time a miserable tract of low ground, bordering the Bay of Biscay.
Plantations, the sinking of wells, drainage and irrigation began to fix
the unstable sands, making fruitful the marsh, creating a healthful
climate and a fertile soil. Early in the 19th century the land here
was sold _au son de la voix_, that is to say, the accepted standard
of measurement was _the compass of the human lungs_. The stretch of
ground reached by a man’s voice sold for a few francs. Crops replaced
the scanty herbage of the salt marsh, and a familiar characteristic of
the landscape, the shepherd on stilts, was seen no more. Six hundred
thousand hectares of Landes planted with sea pines produced resin to
the annual value of fifteen million francs, and through these trees
also was achieved a climatic revolution, and it is this district which
is now a department of a great and well-ordered State.[62]
[62] From Arthur Young’s _Travels in France during the years_ 1788,
1789, with introduction by M. Betham Edwards.
CHAPTER XVII.
VARIETIES OF EPIDERMIS.
Passing now to the smaller trenches of the front line I have chosen as
the first of them a small study of the varieties of epidermis found
in mammals. With the exception of aquatic mammals so few of this, the
greatest vertebrate class, are not clothed with hair that it is only
on the comparatively hairless body of man, with its third of a million
fine hairs, that the varieties of epidermis can be broadly studied.
Much of this chapter will resolve itself into a consideration of the
palmar and plantar surfaces of certain mammals, where no hairy covering
obscures the operation of stimulus and response.
I assume that the foregoing phenomena of hair-direction have chosen
and raised on his shield their own king. But here I must ask of the
succeeding groups when they say, “I am, Sir, under the King, in some
authority,” the question, “Under which King, Bezonian, speak or die”--
Shall it be Darwin’s Personal Selection?
Roux’s Cellular or Histonal Selection?
Wallace’s and Romanes’ Sexual Selection?
Weismann’s Germinal Selection?
The rule of Mendel?
Selection of mutations according to de Vries?
Or shall it be the barbarian king _Plasto-diēthēsis_?
Which indeed of the seven kings will they choose, if I may thus
personify them? I may, perhaps, urge on them the mild and tolerant
rule of Lamarck and Darwin rather than that of the other anointed
sovereigns, hoping this cannot be taken as an attempt to influence the
jury through the Press in a case which is still _sub judice_.
Stimuli and Response.
The skin over the trunk and limbs of man is exposed to stimuli of
pressure, friction, heat, cold and wind in very different degrees,
according to the part which it covers. I do not here refer to nocuous,
or so-called noci-cipient stimuli, as being too casual in their
incidence for the question in hand. Broadly the ventral surface of
the neck and trunk differ much, in respect of the qualities of their
epidermis, from the dorsal. The skin over the former is softer, thinner
and more flexible than the latter, which is in adult life thick, hard
and with larger openings of the sebaceous glands. As the two main
layers of the skin are so closely united it is impossible to state
any general rule as to the parts played in this manufacture by the
epidermis and dermis respectively. Altogether the skin from the dorsal
surfaces of mammals provides a much denser fabric than the latter, and
different qualities of leather are obtained from different regions.
Corresponding differences of texture are found on the extensor and
flexor surfaces of the limbs, especially on the hands and feet. In the
course of his long evolution from a hairy stock, whether simian as we
thought yesterday, or a lower one as Professor Woods Jones suggests
to-day, these dorsal surfaces of neck, trunk and extensor surfaces of
limbs have been exposed through countless generations of men to vastly
more stimuli of friction, pressure, and response, than those of the
ventral and flexor regions. As man’s hairy covering diminished, through
some mysterious and at present unrecognised cause, these stimuli became
increasingly potent in producing a tissue denser than that of the more
protected ventral parts where all forms of these stimuli are slight. I
do not claim that this was a phenomenon that began with man, for in a
measure it was present in those forms which preceded him, and in many
related mammals under the cover of their hairy covering.
When we remember, or conceive what a large portion of each of his
24-hours even in his earliest form throughout life man must have spent,
as he still does, in lying on his back or sides, and in sitting with
his back against a supporting object, and with his gluteal and ischial
regions pressed hard against whatever seat he has selected in cave
or drawing-room, we need not travel far in thought to understand how
great has been the preponderance of stimuli from friction and pressure
on the dorsal and extensor surfaces over those on the ventral and
flexor--and here comes in our familiar “total experience” with stimulus
and response spread over a vast stretch of time. It must be borne in
mind that from the facts of the case a very large number of individual
men and women were exposed to similar, but not the same stimuli at each
stage of the process involved. It is matter of common knowledge that
not only on the palm and sole of man, but on regions where the skin
is not specialised in that remarkable manner that is found in those
regions, but also in others, that increased pressure and friction will
very soon cause a harder and thicker growth of epidermis, as on the
skin over a projecting bone in club-foot, over the shoulder where a
weight is constantly carried, on the knuckles of many manual workers,
and over the patellæ of a devout Roman Catholic, as I have often seen.
On the other hand what conditions more calculated to thin and soften
the skin could exist than those operating on the ventral and flexor
surfaces, axillæ, groins, external genitals and the bends of the elbow
and knee-joints, where pressure, with little friction and greater
warmth and moisture prevails? I need do no more than ask which is the
more reasonable of the two forthcoming explanations of such phenomena,
on the one hand that they are adapted _for_, and on the other adapted
_by_ this experience? I doubt if at any stage of the long process
this slow manufacture of differing fabrics ever conferred on man any
survival value or better matrimonial prospects. At any period or stage
which I have supposed it can only be claimed for the results on the
skin that they did _not_ cause the animal to pass through the meshes of
the sieve, and theoretically might be classed among the _indifferent_
modifications, even if they added a little to the comfort of their
possessor.
Skin of Palm and Sole.
One can examine in more detail the remarkable form of skin which is
found to cover the palmar and plantar surfaces in many mammals. It is
highly specialised and appears in many degrees of efficiency for the
purposes, or uses, of walking and climbing, grasping and discrimination
of objects. With two or three insignificant exceptions these are the
only regions even of man’s body where hairs do not grow in the normal
state, and in most other mammals hair is absent from the component
parts or pads, which correspond to our palms and soles. In the absence
of hairs and sebaceous glands and the presence of as many as 320
sweat-glands to the square centimetre, and especially the papillary
ridges, the mammalian hand and foot present a fruitful field for study.
They have been studied by none more earnestly and thoroughly than Dr.
H. Wilder Harris and Mrs. Wilder Harris (_née_ Inez Whipple). This
small area of skin as an organ for grasping and discrimination has
been studied by persons from different, but not conflicting points of
view. Time would fail me even to mention these, but I would recall
here one aspect of the matter, that is the name given to it by these
eminent authorities, Friction Skin. I think I do them no injustice, nay
even honour, when I claim them as allies for us “Old Contemptibles”
in the struggle, Lamarck _v._ Darwin in respect of these characters
of the “mammalian chiridium.” This is a term employed by them for the
hand and foot of all mammals, and is very convenient for descriptive
purposes. From this point of view this organ has been produced from
more generalised ancestral structures by reason of friction and
pressure, and not for the purpose of resisting them, at least in their
initial stages--again, adapted _by_ and not adapted _for_ meeting those
forces. There are other views of the matter held by Pan-Selectionists,
notably that of Dr. Hepburn, in regard to the papillary ridges. He
would, as I gather, treat them as primarily induced, by selection, for
the better grasping of objects cylindrical or more or less globular.
I have referred elsewhere[63] at some length to this in a book
describing the examination of the hands and feet of eighty-six species
of mammals. The varieties of epidermis were divided into the smooth,
corrugated, scaly, nodular, hairy, rod-like and ridge-covered forms,
also four mixed varieties, such as corrugated with coarse transverse
ridges on the digits, corrugated with papillary ridges, nodular with
papillary ridges, and hairy with coarse transverse ridges and smooth
pads. Of these the species with smooth epidermis and hair are few and
unimportant, and the largest group examined was that of the Primates,
thirty in all, in which papillary ridges were always present. It is
highly probable that the causes of these modifications of the epidermis
in diverse groups of animals could be traced to the habits and modes of
life of each, but I make no attempt here to do this. It is also matter
for inquiry, upon which no agreement has apparently been reached, how
it came to pass that man has virtually lost his hairy coat, and in
regard to the palms and soles of animals, what may be the reason that
so few have any hair on them, and why man has no sebaceous glands, but
has very numerous sweat-glands in these regions.
[63] _The Sense of Touch in Mammals and Birds._ A. & C. Black, 1907.
This is all of great interest, and possibly some day the Mendelians
will solve for us the mysteries thereof. But here I need only ask how
it would have been possible for hairs to grow, or, if growing, not
to be promptly worn away on a surface used by animals from monotreme
to man for walking-pads, and by most of them also for grasping and
discrimination between objects as well. We are so familiar with the
thickening of the skin on the hands of manual workers and on the feet
of those who walk much, to say nothing of what we call a “corn,” from
pressure of tight boots, that we are in danger of forgetting that the
protecting skin over the hands and feet of animals was of necessity
adjusted in a crude way to the measure and kind of walking in past ages
and in all levels of life, and that it is maintained in that adjusted
condition by the use, or disuse, of each life. Another familiar example
is that of knee-pads, as in the gnu and other ungulates. Some such
process it is legitimate to assume whether it be reckoned backwards
to monotremes or later levels of life-forms. We see then before our
eyes how this living tissue becomes adapted in varied ways by response
to the stimuli of friction and pressure, and the modifications thus
slowly effected must, one would suppose, be transmitted to offspring
ultimately from the original groups with which the process began,
when by frequent repetition small changes of structure have arisen at
last. I acknowledge the limited force of the answer, that this picture
involves the continuance in each succeeding generation of the stimuli
which initiated the changes, but the fact remains that _ex hypothesi_
the changes are there, written in tablets of animal tissue, and that
the making-up of an organism in course of many ages is not and cannot
be conceived as being governed alone by the “tyranny,” even in the
_good_ Greek sense of that word, of rigid unit-characters.
In the assumed process the correcting force of the Lamarckian
drill-sergeant is always at hand, as it superintends the construction
of tissues and parts, and I doubt if even Professor Thomson will here
interpose the difficulty of “correlation with useful characters,”
for the only important functions which are invoked as the invariable
antecedent of these structures are the elementary habits of walking,
climbing or grasping objects in certain different ways, and without
these habits or functions there would be neither lemur, monkey nor
man to interest the mind of a biologist from Mars. As I am desirous
of condensing such replies as I can make to certain opinions of
opponents and objections, I will remind the reader that Professor
Bateson in the _Jubilee Volume_ of 1909, pp. 100, 101, uses a metaphor
to illustrate his view that among the facts of nature we meet certain
definite structures and patterns in which we ought not, if desiring
rightly to interpret them, to expect to find _purposefulness_. He says:
“Such things are, as often as not, I suspect rather of the nature of
tool-marks, mere incidents of manufacture, benefiting their possessor
not more than the wire-marks in a sheet of paper, or the ribbing on the
bottom of an oriental plate renders these objects more attractive in
our eyes.” Metaphors are both indispensable and delightful, they are
the very salt of scientific and other sober writings, but they have a
rather “slim” way of betraying their employers. They express at times
the truth too well, and at others when vague and inaccurate lead the
reader right astray. Thinking of this metaphor of tool marks I was in a
modern church the other day and saw just before me a stone pillar the
pediment of which was marked with oblique parallel marks of a mason’s
tool. Here then there were marks left by a human hand at some date or
other and by means of some tool or other. I know one may not reason by
an analogy from inorganic to organic phenomena in which the push and
force of life is in full blast, and that inheritance in the former is
ruled out; but, taking the metaphor seriously, you have to account for
the appearance of the ribbing of paper and the mason’s marks on the
stone. To call them “by-products” or “tool marks” or _obiter facta_,
or by any suggestive name, does not advance the reply to the question,
“Whence came this great multitude?” If I were unwary enough to be here
trying to attack Selection and to respond to the invitation of the more
learned arachnida to walk into his parlour with a scheme of organic
evolution for him to demolish at his leisure, I should have to enter
upon the question of adaptation, specific difference and perhaps other
great disputed doctrines. But, knowing my own limits, and desiring to
keep to the self-imposed limits of the title of this book, I again
plead that I am here contending, as all through it, for the origin
of initial modifications by use and habit, and for nothing else. No
one who reads of the immense amount of research and learning that are
being carried on by the students of Mendelism and Mutationism can fail
to admire them. But, as I have remarked before, these are systems of
thought which in the main deal with characters by distribution or
“unpacking,” as it is called. Such a process of course leads to new
characters by amphimixis, and no one of whom I know denies it. Such
work is concerned with fresh views of the origin of species, but with
lamentable cowardice, or humility, I leave all that great sphere to
those who are incomparably more fit for it, and just seek to mind my
own business.
In subsequent chapters on modifications and their origin I shall not
need to repeat these observations.
Some Chosen Examples of Palms and Soles.
The facts then of a few selected examples of the palms and soles of
mammals are shortly these.
A heavy, burrowing animal, the _earth wolf_ of the Cape, has a very
smooth, hard epidermis covering its foot-pads and is thus a generalised
structure which I have found in no other animal.
The common _mole_ which uses its broad strong fore-feet like a pair
of spades, and depends chiefly for discrimination of its habitat on
the delicate sensory nerve-endings of its snout, has a hard nodular
skin which is much less developed on the hind feet than the fore feet,
the latter being less active tools. It has no papillary ridges, in
accordance with this fact, and is a very efficient miner that never
practises ca’ canny, as we know to our cost when we go out in the
morning and find great heaps of soft earth thrown up in the line of its
advance from its base or fortress. Such a mode of life lends itself
remarkably to the kind of skin on its feet, and this is _now_ at any
rate adapted _to_ its environment.
The _capybara_ is a large, heavily-built rodent, and has rather a
smooth epidermis not specially thick, with long and efficient papillæ
of the corium shown in microscopical sections. Being largely aquatic in
its habitat, and given to frequenting marshy ground and to enjoying as
much sleep as it can manage, it depends a good deal for discrimination
of objects on its sensitive corium, and its epidermis is not much
specialised for, or by friction and pressure in walking. It does not
acquire by reason of stimuli and response any unnecessary tools.
With this may be classed the _echidna_ or Australian ant-eater which
has sparse hairs set on a hard and slightly corrugated epidermis, and,
being mainly a nocturnal animal and living a secluded life, it does not
walk much or far in its stealthy pursuit of worms and insects, and the
stimuli of friction or pressure encountered by it are few.
A similar condition is found on the feet of many small carnivores.
Animals with scales on their feet, which are held to constitute the
earliest stage of the Primate modification of papillary ridges are such
as the _potoroo_, _wallaby_, _kangaroo_ and _giant ant-eater_. Such
scales register a long, long series of stimuli of friction and pressure
in these and their ancestors, in a level of life before any delicate
discrimination of surfaces came into operation.
The nodular form of skin is present in the Canadian _tree porcupine_,
where rough nodules cluster closely on the surface of both feet, and
it is a significant fact that it shares with the American _opossum_
the peculiarity of nodules on the ventral surface of the powerful
prehensile tail. This adaptation tends to efficiency in its arboreal
life, and may well have been produced by infinitely small degrees of
response in structure in the course of a long evolution.
The _rabbit_ alone have I found with rod-like projections of the
epidermic cells, among which are set in dense order the soft, long,
delicate hairs and which thus conduce to its wonderful power of
treading on sharp objects without injury. We thus see the inner meaning
of dear old Brer Rabbit’s jeer of triumph to Brer Fox, “Born and bred
in a brier bush.” This adaptation might be an unit-character segregated
from the ancestral stock of the Leporidæ, or it might not, but at any
rate the rabbit leads a life in which its walking or running is no
more prominent or frequent than is a good “run” on the part of a hunter
which pursues the hare with his beagles, and one may say at least
this--that its mode of life has _not_ produced a hard rough nodular
surface on its feet by stimuli of pressure and friction and response.
One may observe that there’s a divinity doth shape our ends, rough
hew them as we may, even if some objection be taken to the present
view of rough-hewing of parts of our organism on the ground of its
piecemeal character, rather than dealing with the organism as a whole.
To which it may be replied that the Mendelians give high support to the
piecemeal study of the profound subject of genetics, and further that
the business here is to look separately and simply at a few selected
attributes of parts of an organism, and see how they _began_ to grow
big enough to avoid passing through the meshes of the sieve.
The foregoing examples of animals in which papillary ridges are absent
have been given not in their zoological order, nor as representative
of a great many groups, but as taken from the eighty-six species I
examined myself. The following belong to the same series, but all
present papillary ridges in an ascending scale towards perfection in
man.
Examples of Ridge-covered Palms and Soles.
The common _hedgehog_ though a burrowing animal like the _mole_ is
not always underground as his distant relative is. He is not always
mining and though of ancient lineage he is a “slacker” compared with
the mole, hibernating for months, and spending also much time in his
nest and prowling slowly about above ground for insects. He has thus
acquired his somewhat indifferent epidermis that one finds, but with
the addition of sparse papillary ridges. It is the species among this
list with the fewest of these tactile structures, for there are but
three or four separate ridges on six of the ten digits, and radiating
groups on only three of all the palmar and plantar pads. So _quâ_ touch
it is ill-equipped, though it has adapted a higher form of tool than
the rabbit.
The common _squirrel_, that sits much and walks mainly on branches
of trees just as much as it needs to do, has an epidermis little
differentiated, and one which is corrugated with scanty papillary
ridges on the palmar and plantar pads, and none on the digits.
The _squirrel-like phalanger_ which flies always more or less downwards
by a kind of parachute-arrangement has most of its palmar and plantar
skin covered with papillary ridges encroaching upon its corrugated
areas, and a response to more delicate tactile experience has been thus
produced by its intermittent performance of ordinary progression.
_Azara’s opossum_ presents about as large a part of the surface covered
with nodules as with papillary ridges, the latter highly-developed for
an animal so low, zoologically-speaking, but one in which delicate
discrimination is much practised.
The _kinkajou_, another arboreal animal which walks about on trees more
than it uses its feet for prehension, trusting much to its prehensile
tail, shows its corrugated epidermis and papillary ridges developed in
about equal proportions.
These five mammals thus show that the stimuli of pressure and friction
and the response to them are being complicated by the addition of the
more delicate tactile organs known as papillary ridges, and these,
perhaps, in a secondary way are becoming useful in preventing friction.
But I must not omit to point out that, _quâ_ prevention of slipping,
the few sparse papillary ridges of the _hedgehog_, _squirrel_,
_kinkajou_ and _flying-phalanger_, especially those on the extreme tips
of the digits, could have no effect in this prevention and no survival
value. It is otherwise when they are developed in large areas as in the
succeeding groups.
Primates.
All the thirty species of Primates possessed papillary ridges to such
an extent that only small areas of the palmar and plantar skin of the
lemurs showed any other than these remarkable characters. It is so much
a property of the Primate hand and foot to possess these that it might
be almost made a matter of ordinal rank belonging to the Primates, were
it not that a few stray lower mammals also possess it.
The _black-headed lemur_ is the lowest Primate examined and it is
characterised by highly developed patterns of ridges on the palm
and sole, and these are interspersed with nodules on the regions
less exposed to pressure. The complexity of the patterns of another,
the _ring-tailed lemur_, is greater still. Now these nodules are
distinguished from the rough undifferentiated nodules of lower forms,
such as the Canadian _tree-porcupine_, and from the scales in others.
When examined with a lens the separate nodules show small groups of
papillary ridges two, three or four on each nodule, arranged in a
direction parallel to those of neighbouring nodules. They are in fact
papillary ridges in embryo, and shortly above this lemur-stage in
the ascent of animal life they are merged into papillary ridges in
patterns. All this is well told at length by Dr. and Mrs. H. Wilder
Harris. I refer to it here because the disappearance of the rough,
plain, nodular or corrugated epidermis in mammals is coincident with
increasing activity and intelligence in forms who employ or acquire
a more delicate sense of touch in their hands and feet. The cruder
response of structure to stimuli of friction and pressure, evident in
the lower forms, is abandoned in the higher, as tactile delicacy in
prehension comes more into play. Here, for example, may be a subtle
case of the co-operation of the mould and sieve in action.
From this lemur-level the degree of development in the Primate palm and
sole rises and falls, but always advances through the _lemuroidea_,
_monkeys_ and _anthropoid apes_ to man. No attempt at the tracing of
the lineage is made here, and from the present limited point of view
little remains to be said about different Primates. Only two of those
examined will be briefly referred to, the _slow loris_ and man.
The _slow loris_ shares with many monkeys and apes a very soft moist
skin of the palm and sole, and in this and other refinements of this
region it is much beyond many more intelligent, active and higher
Primates. I have never had social intercourse with a _loris_, but
I have shaken the friendly little hand of a _chimpanzee_ with a
combination of pleasure, mild shock and perhaps memories of my own
palms in the more nervous moments of early life. It is a strange,
cool, soft and damp surface, but the sensation conveyed by the skin
of a _loris_ lately dead show that in life it is a wonderfully
sensitive and tender structure. The whole of the palm and sole is
covered with well-developed patterns of papillary ridges especially
on the palmar and plantar pads. No trace of old-fashioned nodules,
scales or corrugation is to be found. The structures due to stimuli
of friction and pressure in its ancestors have disappeared for ever
from this specialised and small group, and we may fairly hold, in
accordance with the law of conservation of energy, that the past is
somehow enwrapped in the present in the strange hands and feet of
the _loris_. The adaptations of the hand and foot of the _loris_ are
most obviously now of value to it in its wary and dangerous life in
the branches of trees, but are equally unfitted for that higher life
which, in his case, consists in going lower down, on the ground. The
extraordinary deliberate life of the _loris_ has been often described.
As he moves from place to place on a branch, fixing one limb before he
moves another, much as we do in going up a ladder, he is subjected much
to the stimuli of pressure, but hardly at all to those of friction.
He sets us a good example of leaving nothing to chance. Thus his soft
sensitive skin suits well his mode of progression, but he would find
the harder, rougher skin of an African baboon very inferior for the
purpose. Here, indeed, I have ventured on the edge of Tom Tiddler’s
ground, and the Pan-Selectionist or Mendelian will make a grab at me
so that I escape with just the loss of a portion of clothing. After
escaping I have only to observe to him as to the adaptations of a
_loris’s_ hand and foot that in human life, of which we know a little,
one can in a measure forecast what a man will be like if we are told
on reliable authority what he and his ancestors have _not_ done in the
way of muscular or cerebral output, without information as to what he
has done. This is too obvious, but also too complex to prove here by
numerous illustrations and it may be left as a mere suggestion as to
the past life of the _loris_ and his ancestors for many generations. He
has _not_ walked in the ordinary method of terrestrial mammals, he has
always moved very slowly about the branches of trees, he sleeps most
of the day in a hollow of a tree, curled up like a ball, and his home
is in moist, tropical regions. No habits and conditions of life could
be better calculated to soften and moisten the skin over his palms and
soles or expose it less to stimuli of friction, while even those of
pressure in his tenacious grasp of boughs are decidedly intermittent.
Unless one may assume the appearance in the distant past of some
unit-character of soft, moist skin in this and other Primates, it seems
difficult to refuse the Lamarckian claim of long, long absence of
effectual stimuli of friction and equally long presence of enervating
“negative” conditions. Proof of such a view is, of course, wanting.
Palm and Sole of Man.
The palm of man’s hand is a miracle of adaptations for touch and
grasping, but has lost most of the coarse structure formed in response
to stimuli of pressure and friction which we saw were common in lower
mammals. This indeed he shares with most simian forms. The skin of
our hands is now very much what we make it and responds very soon to
fresh positive or passive conditions. The horny, cracked epidermis on
palm and digit of the old sailor may be contrasted with the soft and
flexible and pale surface of his twin-brother, the bank clerk, who is
of studious habits and has neither the vice of gardening nor golf. If
one compares the hand of the ordinary maid with that of her mistress
the difference is striking. But if one compares the hand of that
mistress with that of her spinster sister who has lain for twenty years
in bed or on a couch, the difference is equally significant. Indeed the
sofa-and-bed-ridden invalid, of whom I knew a few once, but who have
gone out of fashion, gives the observer some useful thoughts as to the
why and wherefore of the strange skin of the hands of the _slow loris_
previously referred to. And if he be disposed also to the pleasant
pursuit of moralizing at the expense of others he will feel led to
reflect over harshly on the invalid and compare her outlook on life
with that of the _loris_. Even in this concrete case of the hand of an
invalid there may be evidence of positive as well as negative response,
if one examines the right forefinger so much used in sewing, where the
skin becomes hard and thick.
The foot of man has a good deal of negative evidence in favour of my
contention as well as positive. As to the latter, in the thickening of
the skin over the heel and ball of the great toe in those who walk much
we find changes precisely similar to those on the hand. The negative
or degenerative changes visible on man’s foot consist chiefly in the
remarkable simplicity of pattern of the papillary ridges as well as
their flattening and blurring, through wasting of those which occupy
mainly the arch of the foot. These will be shown in the next chapter
in a drawing. When this portion of skin is compared with that of the
foot of any monkey or anthropoid ape it is clear that in this respect
the skin of man’s foot has undergone even more degeneration than his
hand has shown of higher development. This degeneration has coincided
with two facts, first that man’s terrestrial locomotion has advanced
far beyond that of any other Primate, and second, that he alone has a
plantar arch. This subject belongs to a later chapter and is referred
to here because the possession of an arch to his foot has caused man to
escape, on the under surface of it, a vast proportion of the stimuli of
pressure and friction involved in his mode of walking, and the extreme
simplicity of his plantar papillary ridges, and relatively thin, soft
skin under the plantar arches affords a fairly conclusive example of
change of structure from disuse _per se_.
I have thus only selected and used two striking types of the Primates,
the _loris_ and man, not wishing to burden this part of the subject
unduly with intervening and less characteristic forms of life. It
may be legitimate here to say in defence of this long chapter that
it illustrates what I desire to keep before me all through, the fact
that use, habit, environment and selection go ever hand in hand. In
all matters of science one has to descend to particulars, so it seemed
necessary to select a few scattered phenomena in the best known groups
of higher animals and endeavour to understand how certain “characters”
or better “modifications” _began_ to grow big enough to avoid passing
through the meshes of the sieve.
CHAPTER XVIII.
ARRANGEMENT OF THE PAPILLARY RIDGES.
The subjects of the preceding, present, and the succeeding chapter
are closely allied, from the fact that they all deal with structural
changes in the mammalian skin, and that most of these are exhibited for
us on our own palms and soles. They certainly comply with the canons of
Henri Poincaré as to simplicity, regularity and chance of recurring.
In the last chapter, papillary ridges as organs of touch were briefly
referred to, but their mode of development into complicated patterns do
not concern the questions here at issue. The general manner in which
they are arranged on the hands and feet of man and the Primates below
him is very much a matter for such Lamarckian methods of inquiry as I
have chosen. In this examination of the ridges I will proceed from man
backwards among the Primates and lower still. I described these ridges,
in a book previously referred to in the following words, and find no
need to alter them here. “The ridges and adjoining furrows which cover
the palmar and plantar surfaces of all Primates and a few lower forms
in smaller degree, may be compared to the ridges of a ploughed field
over which some object, as a light roller, has been passed, the effect
of this being to produce a series of ridges with flattened tops. This
can be well seen with a lens when the ridges are examined in profile,
and is their normal condition in man and many lower animals, in nearly
all the palmar, plantar and digital regions.”[64] The reservation in
the last sentence is not material here.
[64] _Sense of Touch in Mammals and Birds._
The Hand of Man.
[Illustration: Fig. 59.--W. K. Right hand drawing of papillary ridges,
made from impressions.]
Beginning with the tips of man’s fingers and excluding the wonderful
patterns which Galton did so much to elucidate and bring into order,
we find the ridges are placed, to a remarkable extent, parallel with
the skin-flexures which will be treated in the next chapter. I term the
thumb and fingers D 1, 2, 3, 4, 5 for the sake of accuracy (Fig. 59).
Over the last joints (distal) of all the digits the ridges suddenly
diverge from their directions in the patterns of the pulps, and become
arranged transversely to the axis of the digits. This arrangement
is observed on the remaining segments of the digits except, very
significantly, on the outer or radial side of D 2 and the inner or
ulnar side of D 5 where they slope more or less towards the palm. Their
lines thus cross slightly those of the skin-flexures in these small
areas. On the radial side of D 1 this slope appears in a minor degree,
but here it coincides with those of the flexures. On the palm are
similar arrangements of the ridges near the radial and ulnar borders,
and especially on the two great eminences, thenar and hypothenar,
also at the bases of digits 2, 3, 4 and 5. Over the rest of the palm
they are arranged in a longitudinal or oblique direction. These brief
descriptions are enough to show the close correspondence of the
arrangement of the ridges with the flexion of the numerous joints of
the hand. An observer can demonstrate this by holding up the open hand
in a good light and flexing the fingers slightly, which brings nearly
all the ridges adjacent to the joints into directions parallel with one
another, the greater lengths of D 3 and 4, and their closer functional
connection with one another, producing thus a transverse arrangement,
and in D 1, 2 and 5 a more oblique one. In the palm this correspondence
of ridges with flexion lines of joints is not found so much except in
the central part of this surface. But the oblique and longitudinal
ridges of the palm where it becomes concave in the action of folding
the hand over a globular object are well shown there also to correspond
with such action.
This general grouping of ridges is seen, _mutatis mutandis_, to belong
to all the palms and soles of lower Primates, and the illustrations
given will speak for themselves, so that little need be said on each.
Reasons for Arrangement Observed.
When one discusses the forces in action on man’s hand which are claimed
to have thus arranged the ridges, in regard to the question of use and
habit, little more need be added as to those of other Primates, and it
is because we know more about ourselves than them, and our own palms
and soles are available for inspection, that I have taken man as the
example.
The main question is the old and now familiar one: “Are these ridges
arranged as we see them _by_ use and habit, or adapted _for_ use?”
Dr. Hepburn and the orthodox Selectionist would say that, of course,
their mode of arrangement is an adaptation governed by selection for
preventing slipping in the action of grasping an object by the hand,
and in the foot for preventing slipping in walking. This does not take
into account the question as to how the original slight shifting of the
ridges in the earliest man and in lower forms could have had selective
or survival value, for example, the insignificant sparse groups of
ridges on the palm, sole and _tips_ of the digits in a hedgehog or
squirrel. As things are now they _do_ subserve these purposes. But I
think this matter of prevention of slipping has been much exaggerated,
though I may be told that this is a matter of opinion and not a valid
argument against the hypothesis.
Foot of Man.
[Illustration: Fig. 60 S. K. Right foot drawing of papillary ridges
made from impression.]
The point may be best understood by considering the foot of man, of
which Fig. 60 shows a good example. The value of the roughened surface
of the foot with its papillary ridges can hardly have been great, even
in the days when man’s foot was naked, at any rate so little that for
him to acquire by a selectional process such a remarkable _change_ of
arrangement as we see when we look at the foot of man and of any other
Primate involves on our part a tremendous stretch of imagination as to
its _modus operandi_. These low, soft ridges of man’s foot could do
little to prevent him from slipping on such surfaces as grass, sand,
rock, wet or dry, and from the time when he began to protect his feet
with coverings this small value would be further reduced. _Underneath
his developing plantar arch it would not exist at all, and yet here
especially he has changed their direction._ As to the papillary
ridges, man’s foot has sadly embarked on the pathway of degeneration
much as his little toe has done. Not only has he here a much simpler
arrangement than any ape or monkey, but the individual ridges are
blurred and flattened on much of the plantar surface. This comes of
his pride in acquiring his human distinction, or title of nobility, of
a plantar arch and his coincident increase of pedestrian locomotion.
On the triple bases of support, heel, ball of great and little toe,
the ridges are still strongly marked and coarse; transverse on the
heel, whorl-like on the ball of the great toe, and oblique or nearly
transverse on that of the little toe. On the rest of the surface they
are vulgarly transverse. And I may add that the toe-prints of man are
simplicity itself compared with his finger-prints. It would seem that
this example of arrangement of ridges on man’s foot is strongly in
favour of the hypothesis that they are so disposed by flexion of the
foot in walking, and not by some need for prevention of slipping under
the guidance of selection.
Lower Animals.
[Illustration: Fig. 61.--Slow loris--right foot.]
At the other end of the scale the scanty ridges of a hedgehog’s or
squirrel’s foot would be negligible in preventing slipping, however
useful they would be, as I hold, as early organs of touch. Between
these extremes the _slow loris_ affords a valuable example to study,
with the help of Fig. 61. The foot, as more concerned with prevention
of slipping than the hand, is chosen for observation, but with little
exception the hand agrees closely with it. On the tips of four digits,
D 1, 3, 4 and 5, omitting D 2 for the moment, the ridges are arranged
nearly in a longitudinal direction, and would on that account have
little or no effect in preventing slipping of the foot. If this be
disputed one can but reply that if the need of preventing slipping
in this tiny area were to call forth selective value this is not the
arrangement of the ridges that best serves the purpose. It may be
remarked here that the pulps of _lemurs_, the _marmoset_ and _squirrel
monkey_ all show this indifferent mode of grouping of ridges. The
aborted D 2 of the _loris_, with its hooked nail overhanging the
circular pattern of ridges, is obviously quite unadapted for any
non-slipping effect of its skin, as a glance at the figure shows. On
the remaining segments of the digits the ridges in the main slope from
each side of each digit in the distal direction and fail here also to
obtain the best, or transverse direction for preventing slipping in
locomotion. The corresponding surface of D 1 is not different from its
pulp as to direction of ridges, and it is here to be noted and admitted
that when this muscular great toe is tightly applied to a branch,
which from its shape it must cross at a right angle, the non-slipping
effect of the longitudinal ridges would be very effective. One must
then notice that over the middle of the sole of this foot the ridges
have again changed their direction and lie in a transverse direction.
Between this and the basis of the digits are three fleshy pads and an
intervening area of longitudinal ridges.
The first question that arises in the attempt to analyse so complex a
grouping on a strange member like the foot of a _loris_ is this--what
is the primary function subserved by the ridges and their mode of
arrangement, and what may be their secondary uses? In the book
referred to I have maintained throughout, in opposition to Mrs. Wilder
Harris and others such as Dr. Hepburn, that the sense of touch is the
primary, and prevention of slipping the secondary adaptation secured
by the ridges. If this be true (and I know it is _sub judice_) there
is a very clear reason why the ridges should be longitudinal on the
tips of the digits on account of the better discrimination of small
objects secured by this arrangement, though it does not well assist
the _loris_ to avoid slipping. On D 1, as mentioned, the non-slipping
effect is secured by its ridges, and this digit is necessarily less
employed for discrimination than support. On the other hand the sloping
arrangement on the rest of the segments of D 3, 4, 5 is decidedly less
effective in preventing slipping than a transverse arrangement would
have been. I think I am justified in saying that too much has been made
of this secondary effect of the ridges in the prevention of slipping.
I know that the string wound round the handle of a cricket bat is very
effective for its purpose, but one can also understand that a casual
strand wound here and there on the handle as the ridges are on a
_hedgehog’s_ and _squirrel’s_ hand and foot would be of little use for
the purpose.
On the other hand if the view may be entertained that on the palm and
sole of _hedgehog_, _squirrel_, _loris_ and man, we have written in
rows of papillary ridges and their modes of arrangement a register of
long-continued flexion of hand and foot in flexion and correlated
actions, we find the facts of these and numerous other Primates agree
in a remarkable manner with the hypothesis; whereas the exclusive
non-slipping rival has many awkward facts to explain, or disregard.
Further as one has always to bear in mind the Mendelian analysis it
should be observed that the extreme variability, within certain limits,
of the arrangements of papillary ridges throughout the Primates renders
the hypothesis of unit-characters segregated, according to Mendelian
laws, wholly inapplicable to the _manner of their arrangement_ even
though perhaps not so to the _existence_ of papillary ridges.
[Illustration: Fig. 62. Hedgehog--right foot.]
[Illustration: Fig. 62A. Hedgehog--right hand.]
[Illustration: Fig. 63. Common squirrel--left foot.]
It may be bluntly asserted that the ridges are arranged as we find them
because, hands and feet being used as they are, the ridges “can do no
other,” and that there’s an end of it, and that we cannot derive any
help as to the origin of specific difference from such a trifle, the
next item on the agenda should be called for. As a piece of dialectics
that would be effective, but if taken literally it only goes to prove
my simple contention.
It will be enough to mention the hand alone of the remaining series
with a note as to each animal.
Fig. 64 gives the hand of a _chimpanzee_ with ridges on the pulps
resembling those of all the _apes_, _monkeys_ and _lemurs_, arched
groups on the digits and longitudinal ones on the centre of the palm,
both of these last two being exactly what would be found arising from
the actions of climbing branches and discriminating globular objects in
the palm.
[Illustration: Fig. 64.--Chimpanzee--right hand.]
[Illustration: Fig. 66.--Orang--right hand.]
Fig. 65 is that of a _gorilla_ and its general features resemble
closely those of the _chimpanzee_ and of Fig. 66 which is that of an
_orang_.
[Illustration: Fig. 65.--Gorilla--left hand.]
[Illustration: Fig. 67.--Gibbon--left hand.]
Fig. 67 of a _Hainan gibbon_ is very different on the palm from the
other three apes for its ridges are nearly all longitudinal or
slightly oblique, precisely as one would find this part if the _palm_
were used very little for grasping boughs and much for discriminating
globular objects procured for its repasts. The wonderful long digits
of the gibbon form its main organ for supporting itself on branches
and swinging its body rapidly from branch to branch, and the arched or
nearly transverse ridges on the digits are placed just as the endless
use of them for this purpose would be likely to follow from it. This
example is a very clear one for showing, if it exist, the effect of use
and habit on the disposition of the ridges.
Fig. 68 shows the arrangement of papillary ridges in a _lemur_ and 69
that of a brown _sapajou_.
Fig. 70 of the _Chacma baboon_, playfully called by the Boers Adonis,
is a very active and wary animal which lives on the rough rocky slopes
of the Cape. It is very much of a pedestrian and the response of its
mode of life and use of its forefoot is shown in five great pads of
muscle and efficient whorls of ridges for touch, those on the digits
being very nearly all transverse in accordance with simple flexion of
these joints. This again is what one would expect if my hypothesis be
sound. The purely non-slipping mechanism supposed by the rival view is
not here well supported by the facts.
[Illustration: Fig. 68.--Left foot of ring-tailed lemur.]
[Illustration: Fig. 69.--Brown sapajou, right hand.]
Neither the arrangements of ridges (Fig. 61), in _loris_, nor the
_hedgehog_ (Fig. 62), nor the _squirrel_ (Fig. 63), need further
reference, but they are all, I think, very consistent with the
prolonged effects of use and habit.
Some Undesigned Experiments in Ridges.
This section of the subject has afforded a good supply of indirect
evidence, but so far no direct proof that papillary ridges can be
created and disposed in their lines by pressure, friction and response.
The clearest case is one I brought forward at the Zoological Society
of London in 1905, and which was published in its proceedings of April
18th. It was an instance of the hand of a _chimpanzee_ with papillary
ridges produced in an aberrant or abnormal situation by walking, and
was given as follows:--
“In the course of an examination of the papillary ridges in some
specimens of anthropoid apes and monkeys certain groups of ridges
were found on the _extensor_ surface of the terminal phalanges of
the hand, apparently identical with those of the palmar and plantar
surfaces. Three specimens of chimpanzee living in the Society’s
menagerie were examined, of the ages: one year eight months,
two-and-a-half years and six years. In the oldest of these, called
“Mickie,” the ridges were definite and well-developed, on the second,
third and fourth digits on both hands; in the youngest specimen,
“Jack,” they were absent; and in “Jimmie,” two-and-a-half years old,
they were small and ill-defined, as if in process of development.
Direction of Ridges.
_Mickie._ Ridges longitudinal and reaching to the matrix of
the nail on the second, third and fourth digits.
_Jimmie._ Showed ridges as follows:--
R. hand 1st D none. L. hand 1st D none.
2nd " oblique. 2nd " oblique.
3rd " transverse at base of D. 3rd " "
4th " " " " 4th " "
5th " nearly longitudinal. 5th " none.
_In these three specimens ridges were absent from the corresponding
surfaces of the foot._
“The well-defined longitudinal direction of the ridges in “Mickie”
is worth notice. It must be remembered in this connection that a
chimpanzee walks with the extensor surfaces of the phalanges touching
the ground and the digits turned inwards, so that their long axis
are at right angles to the line of progression of the animal, and
accordingly the ridges of this part also occupy the same relative
position. There is no correlation in this instance between the act
of prehension and the direction of the ridges, though it agrees
closely with the general rule which obtains in so many regions,
that the ridges lie at right angles to the line of incidence of the
predominating pressure on the part.”
In this example of ridges developed on an abnormal situation we see
what is, perhaps, an undesigned experiment as to the production of
ridges by a more frequent habit of walking in captivity than would
be found to occur in the wild state, for, as Lydekker says in the
_Royal Natural History_, Vol. I, p. 27, “When the chimpanzee goes
on all-fours, he generally supports himself on the backs of his
closed fingers rather than on the palm of the hand (see Fig. 6 of the
illustration on p. 15) and he goes _sometimes_ on the soles of his feet
and _sometimes_ on his closed toes.”
[Illustration: Fig. 70.--Left hand of chacma baboon.]
I have underlined purposely this word “sometimes,” for in the instance
I have described, not only the presence of the ridges and their
direction on the backs of the fingers but their absence on the backs of
the toes is significant, and I suggest that the _chimpanzees_ examined
have not sufficiently often exposed the backs of their toes to pressure
and friction for the production of ridges, whereas those on the backs
of the fingers have done so. Another point worth notice is that in the
oldest of the three _chimpanzees_, “Mickie,” æt six years, the greatest
number of ridges is present; in “Jimmie,” æt two-and-a-half years, they
were “small and ill-defined as if in process of development,” and in
“Jack,” æt twenty months they were absent. This would agree at any rate
with the hypothesis that the element of time and frequent repetition of
stimuli enter into the causation of aberrant ridges.
A similar condition, with aberrant papillary ridges, has been found on
the digits of the hand of the _orang_.
On the heel of adult man ridges are found surrounding it, of the
average depth of one inch from the plantar surface, and in one
particular case of a woman aged forty-nine, the depth of this area on
each foot measured was one and a half inches from the plantar surface.
The extensor surface, or back, of the little toe shows ridges when it
is distorted by ill-fitting boots.
In man ridges frequently appear on the radial side of the back or
extensor surface of the index finger to nearly the middle line of the
finger, and this is often more on the right than the left hand.
CHAPTER XIX.
FLEXURES OF THE PALM AND SOLE.
Those flexures of the palmar and plantar skin which are called by
Galton chiromantic creases, and said by him to be no more significant
to others than palmists than the creases of old clothes, have received
a remarkable amount of pseudo-scientific attention since earliest
times in Chinese and Greek history. The former even added podoscopy to
their chiromancy. The line of life, the line of the head, the line of
the heart, the line of fortune and that of the liver, figure freely
in fortune-telling of modern drawing-rooms by women who ought to be
in Holloway gaol, but are not. The gipsies, their predecessors and
equally honest teachers, did not employ such high-sounding words, but I
believe that by observing closely the bearing, looks, dress and manner
of their dupes, while pretending to study their palms, both classes of
practitioners, like phrenologists, are able to tell a good deal of what
their customers _are_, and being shrewd persons they are able to guess
pretty well what they _will be and will do_.
I agree with Galton that these creases of hand and foot are no more
significant than those of an old coat-sleeve, a pair of trousers, or
boots; but they are not less significant of certain muscular habits of
the wearers of those articles.[65]
[65] Galton might have referred by way of illustration to an immortal
woman in _Martin Chuzzlewit_, who shall be nameless here.
The flexures in question are in line with the subjects of the two
preceding chapters, and require little more description in detail than
is afforded by the accompanying illustration of mammalian hands and
feet.
Description of Flexures.
There are two classes which may be conveniently called here Primary and
Secondary, the latter being too variable and accidental for further
notice. The former lie in three main directions and are longitudinal,
oblique or transverse. They represent in graphic characters the nature
and degree of the functions exercised by muscles moving the joints
which underlie them, and are often called “flexion-lines.” They are
“folds so disposed that the thick skin shall be capable of bending in
grasping while it at the same time requires to be tightly bound down
to the skeleton of the hands and feet, so as to prevent slipping of
the skin which would necessarily lead to insecurity of prehension,
just as the quilting and buttoning down of the covers of furniture
by upholsterers keeps them from slipping. For this purpose the skin
is tied by fibres of white fibrillar tissue to the deep layer of the
dermis along the lateral and lower edges of the palmar fascia and to
the sheaths of the flexor tendons. The folds, therefore, which are
disposed for the purpose of making the grasp secure, vary with the
relative lengths of the metacarpal bones, with the mutual relations
of the sheaths of the tendons and the edge of the palmar and plantar
fascia.... The sulci are emphasised because the subcutaneous fat,
which is copious in order to pad the skin for the purpose of holding,
being restricted to the interval between the lines along which the
skin is tied down, makes these intervals project, and these are the
monteculi.”[66]
[66] A. Macalister, _Palmistry Encycl. Brit._, 11th Edition.
This account of them from a leading anatomist shows that not for
nothing have these creases been evolved. They are inherited, have an
important function and are worthy of study in their humble way: they
may be even dignified with the name “character.”
They are often double over the joints of the fingers and toes, but,
from the functional point of view and for simplicity, may be reckoned
as single.
Chief Types.
[Illustration: Fig. 71.--Flexures on palm of right hand. Drawing made
from impression.]
The most common types of them in the hand of man are shown in the
example given in Fig. 71.
1. A flexure over each phalangeal joint.
2. A flexure at the bases of the digits.
3. A flexure over the metacarpo-phalangeal joints of D 2, 3, 4 and 5
with an oblique direction, called _linea mensalis_.
4. A flexure over these same joints and oblique in direction, but
nearer to the wrist--the _linea cephalica_. These flexures 3 and 4,
though arising from the flexion of one set of joints should be looked
at as separate folds because of their time-honoured popular names.
5. A curving flexure surrounding the thenar eminence, extending from
the centre of the wrist along the palm and terminating at the radial
border.
6. Variable longitudinal and oblique flexures not specified, which I
have called secondary.
[Illustration: Fig. 72.--Foot of common squirrel.]
[Illustration: Fig. 73.--Flexures on foot of vulpine phalanger.]
[Illustration: Fig. 74.--Foot of loris.]
[Illustration: Fig. 75.--Foot of ring-tailed lemur.]
Meaning.
Whatever be the meaning and origin of these flexures they are not mere
folds such as one makes in a garment and leaves it so. Action, function
and fitting of the structures of the hand and foot are involved in
their history. They may loosely be termed “ergographs” without any
reference to the exact measurement of work done. No proper idea can
be formed of them if the original function and evolution of the
walking-pads of earlier mammals be omitted. If one goes back and back
until one reaches some lowly marsupial as a _vulpine phalanger_, or
insectivore such as a common _hedgehog_, one may even metaphorically
see these animals being fitted by a shoemaker with rude shoes or
walking-pads for the better locomotion on or under ground, or in the
branches of trees. These pads are projecting masses of hard fat with
fibrous tissue interspersed and they early become fitted or adapted
_to_ or _by_ the use to which they are put. It is impossible to suppose
that certain rudimentary pads are devised by selective processes prior
to the altered habits of walking of the animal that acquires them. From
the shoemaking point of view the fashion is rough and generalised, and
the changing habits of the animal adapt the shoe by degrees to the
function employed, much as many a private soldier knows to his cost
that he has had to adapt slowly and painfully his army boot to his
particular foot. This process in an early pedestrian mammal involves
the breaking up and limiting of the rudimentary pads by sulci in the
dense skin, and the process of struggle and adjustment between the
pads and their bordering furrows issues in the characteristic flexure
of each mammal. From experiences in the human body one knows how
easily fibrous adhesions between the skin and deeper parts, notably in
cases of Dupuytren’s contraction of the palmar fascia, are formed by
close apposition of the two layers. Such adhesion is precluded when
much movement of the part occurs, but _ex-hypothesi_ the rudimentary
flexures are distinguished by absence of movement, and the conditions
for fixing down the deeper layers of the skin to the bones beneath are
clearly present. That these are not indifferent structures is evident
from what Macalister says, and though they be small or even trivial may
be held to have acquired at some time or other selective value. Their
early stages would necessarily be too tentative, varied and slight to
acquire such value.
[Illustration: Fig. 76.--Foot of squirrel-monkey.]
[Illustration: Fig. 77.--Foot of macaque.]
[Illustration: Fig. 78.--Foot of gibbon.]
[Illustration: Fig. 79.--Hand of chimpanzee.]
Fig. 72 is a sketch of the hand and foot of a squirrel (Sciurus) and
the numbers 1, 2, 3, 4, 5 and 6 are placed conspicuously on the walking
pads in accordance with the teaching of Dr. and Mrs. Wilder Harris as
to the six palmar and plantar walking-pads, of which the typical palm
and sole is constructed. The thick, black lines indicate the flexures
formed round the pads by the exercise of the functions of the hand and
foot.
Fig. 73 represents the clumsy, thick walking-pads of a marsupial the
vulpine phalanger, _trichosurus vulpecula_.
Fig. 74, the highly-developed prehensile foot of the loris.
Fig. 75, the foot of a ring-tailed lemur.
Fig. 76, the foot of a squirrel-monkey (Chrysothrix Sciurea).
Fig. 77, the foot of a macacus (Macacus cynomologus).
Fig. 78, the foot of a gibbon.
Fig. 79, the hand of a chimpanzee and here the resemblance to the
_hand_ of man and _not to the foot of man_ is very striking.
A description has already been given of man’s flexures of the palm.
[Illustration: Fig. 80.--Drawing of flexures of sole of foot in young
adult.]
Fig. 80 is a careful drawing of the sole of a young active woman
with a well-formed foot, and there is little typical in the mode of
arrangement of its creases except the slight tendency to transverse
lines of flexure. In all the feet I have examined I have found no
single flexure that is constant, and the longitudinal ones here shown
are often absent.
Reviewing these examples one observes an evolutional decay of a minor
but necessary piece of mechanism of the Primate hand and foot. The
general similarity, _mutatis mutandis_, of the flexures of the palm
and sole in Primates is very noticeable, and is associated with the
strong prehensile power of the foot of all the forms below man. In
the cases of the two apes shown in this series, the resemblance is
still well marked, more so even in the chimpanzee than the gibbon, so
that the disappearance from the sole of man’s foot of any important
flexure is very significant of his loss of prehensile and gain of
locomotive perfection, and I find it impossible to conceive any process
of evolutionary change where a loss of the flexures of a prehensile
foot could come under the power of selection, on its own merits. On
the other hand this remarkable instance of disuse of a formerly useful
structure is adequately accounted for by the evolution of an organ
like the human foot which in course of long periods of time became an
organ of one function. Weismann might score a point over Spencer from
his laboured explanations of man’s dwindling little toe, but here,
I submit, he would have had to take refuge in silence, and pass to
characters of a higher and more debateable kind.
CHAPTER XX.
THE EVOLUTION OF A BURSA.
A bursa exercises a function in the animal body which is the direct
opposite of that shown to belong to the flexures of the hand and foot.
Whereas the latter are adapted to the prevention of slipping in the
act of prehension, bursæ are delicate contrivances for producing the
maximum effect of sliding, within certain limits, between two opposed
surfaces, either between the skin and a hard surface beneath it,
between two muscles, or a tendon as it moves over a bone. As they are
very variable and most of them are inherited and congenital, while
some are produced only in the lifetime of the individual, they are
useful for consideration in regard to the questions of transmission of
modifications and of the origin of initial variations. Their degree
of utility ranges, for example, in man, from that of the prepatellar
bursa without which no useful movement of the knee-joint is imaginable,
to the insignificant bursa which may or may not be found on the
dorsal surface of a phalangeal joint of the foot. The principle laid
down by Lyell, to which allusion has been made elsewhere, that is,
of “explaining changes in the surface of the earth by reference to
causes now in action,” is applicable in this small department of the
evolution of a minor structure of the animal body. As man furnishes the
largest of all collections of these lubricating organs, his skeleton
and skeletal muscles will form the main subject of this chapter, and I
venture, if one may say so, to “Lyell” them. None of the sections of
this book except that on the mammalian hair affords so simple and easy
a field for watching in operation certain mechanical forces. We may
here go down to the potter’s house and watch him moulding his clay, or
the cobbler his leather. So much are bursæ in the human body under the
power of extraneous forces that I venture to say that if some young
surgeon of an inquiring mind were to choose a place and time when the
Honourable and Vigilant Stephen Coleridge was out of the way, and were
to produce in a young _chimpanzee_ under an anæsthetic a “greenstick
fracture” of his radius and ulna, immobilising it at a right angle
for a month, the animal would exhibit at his death some years later a
highly developed bursa over the bony protuberance nearly as good as
the olecranon bursa on the uninjured side, and better than that of the
injured limb. As I have reason to know the meticulous vigilance of this
professional and expert humanitarian I hasten here to say in advance
that I do not recommend this experiment, not because it would not be
entirely justifiable, but because nature herself in the highest Primate
has produced many undesigned experiments of nearly equal value, as I
hope to show.
Bursæ Described.
Broadly considered a bursa is a sac lined by synovial membrane, and an
extreme example of the simplest form in which it is found may be said
to be that of the condition found in a domestic dog. Under its skin,
except on such regions as the snout, the tail and the feet, there is
hardly a place where a bursal surface does not exist. Here and there
trabeculæ may divide the great sac imperfectly, but from the protective
and selective point of view this mechanism under a dog’s skin may be
compared to the oil with which an Indian criminal lubricates his naked
body so as to elude capture. To us who are too familiar with dog-fights
(to which the Hon. Bertrand Russell likened the recent Great War, as we
all remember) and who know how much noise and ferocious attempts are
made by the warriors to bite one another, and how little success they
achieve, the beautiful adaptation of nature in the dog far surpasses
that of the Indian criminal. Indeed the latter may well have been
suggested by the former.
Between such a simple and undifferentiated bursal surface as this and
another such as the small but essential bursa under the tendo achillis
there are endless variations adapted to particular uses and regions.
The description of bursæ given by Macalister is too clear and good not
to be given in his own words.[67]
“Synovial membranes are found either as the lining of joints, or as
_Bursæ_, which are closed sacs (_a_) between contiguous soft parts,
or (_b_) beneath soft parts which glide tensely over a bone. Bursæ
are formed around and beneath tendons in the neighbourhood of joints;
and the hard part on which the tendon plays is often invested with a
layer of cartilage over which the synovial membrane does not extend.
When they completely surround tendons, as in the finger and toes they
are called _thecæ_ or sheaths, and the tendons are connected to the
sheaths by synovial reflections. Sometimes bursæ lie between exposed
areas of skin and projecting bony points, such as the patella,
olecranon, ankles, etc.
“Their (synovial) membrane differs from the synovial membrane of
joints in not having so continuous or definite an endothelial lining;
indeed, while some bursæ, such as that beneath the ligamentum
patellæ, have a more or less regular lining of regular endothelium,
others have only elongated connective cells forming an imperfect
lamella, and there are all possible gradations met with between
the regular saccular bursa, and a loose meshwork of areolar tissue
of which the bursa is only a specialisation. Bursæ may be (1)
subcutaneous, (2) subfascial, (3) between two tendons, or (4)
between tendons and subjacent ligaments or bone. Of these, some
communicate with the neighbouring joints always, some occasionally,
and some never. Bursæ underlying parts which have an extensive range
of motion are _unilocular_, with a single cavity. Bursæ spread
over an extensive surface, and whose walls move but little on each
other, are often divided by imperfect fibrous septa, and are called
_multilocular_. Almost all the lesser bursæ are unilocular, most of
the subcutaneous bursæ are multilocular.”
[67] _Text Book of Human Anatomy._ A. Macalister, 1889, p. 48.
Now if one were not engaged upon such a problem as that of initiative
in evolution and in trying to give examples of it there would be no
Gordian knot to cut, and the condensed statement of Macalister might
be simply taken as an accepted account of the manner in which reading
between the lines a bursa is formed in the animal body. But, when an
hypothesis such as the present is in question, one may not cut the
Gordian knot in this way, and must produce briefly certain observations
of the process, not only those known in man by anatomists and surgeons
but also some found in lower Primates.
Human Bursæ Enumerated.
The following is a list of bursæ in man of which some are normal
or always present, and others which are both occasional in their
appearance and often imperfectly developed.
_Front of Neck._
(A) One in front of the pomum adami.
(B) One in the thyro-hyoid space extending to the under surface of
the hyoid bone.
(C) One beneath the stemo-hyoid muscle.
(D) One above the hyoid bone.
_Pharynx._ A small central pit constituting a single bursa the _bursa
pharyngea_.
_Behind the angle of the lower jaw._ One.
_On the symphysis of the chin._ One.
_On the Acromion process._ One.
_Beneath the deltoid_ and the acromion process, one large bursa often
opening into the shoulder-joint.
_Elbow._
(A) One over the olecranon.
(B) One occasionally over the inner epicondyle.
(C) One over the internal condyle of the humerus.
(D) One over the external condyle of the humerus.
(E) Small one between the biceps tendon and the head of the radius.
(F) Often a second bursa which separates the tendon from the oblique
ligament crossing it.
_Wrist._
(A) One over the styloid process of the radius.
(B) One over the styloid process of the ulna.
_Hand._
(A) One over each of the metacarpo-phalangeal joints.
(B) One over each of the phalangeal joints.
_Region of hip._
(A) One over the anterior superior spine of the ilium.
(B) Large one between the great trochanter and the gluteus maximus
muscle.
(C) One between the gluteus medius and the bone.
(D) One between the gluteus minimus and the bone.
(E) One between the psoas and iliacus muscles often opening into the
hip-joint.
_Thigh._
(A) One over external condyle of the femur.
(B) One over internal condyle of the femur.
_Knee-joint._ The prepatellar bursæ.
(A) Between the skin and superficial fascia at the lower edge of the
patella there is often a small subcutaneous bursa.
(B) Beneath the superficial fascia over the fascia lata there is
always a large interfascial bursa, intersected by smooth fibrous
bands extending downwards over the upper part of the patellar
ligament.
(C) One still deeper between the deep fascia and front of the bone
there is a layer of lax connective tissue.
(D) Sometimes a third or deep subfascial bursa.
“These bursæ over the knee-joint appear in fœtal life and vary in
size in persons of different occupations, being often large in
housemaids and carpet-nailers, and often communicating with each
other.”[68]
[68] Macalister, p. 488.
(E) Occasionally the upper part of the synovial pouch of the
knee-joint is shut off from the general cavity and forms a separate
bursa beneath the extensor muscles. It always communicates with the
knee-joint though originating independently.
_In the Ham._
(A) Large bursa between the inner condyle of the femur and the
gastrocnemius muscle, often opening into the joint.
(B) A smaller one on the outer side.
(C) One between the biceps tendon and the external lateral ligament.
(D) One between the semimembranosus }
(E) One between the popliteus }
(F) One between the sartorius } and the bone.
(G) One between the gracilis }
(H) One between the semitendinosus }
_Tibia._
(A) One over the tuberosity.
_Ankle._
(A) Over both malleoli.
(B) Between the tendo achillis and the os calcis.
_Foot._
(A) Over plantar surface of the great toe.
(B) Over plantar surface of the little toe.
(C) Over the dorsal surfaces of all the phalangeal joints of the toes.
(D) Over the dorsal surface of metatarso-phalangeal joint of the great
toe.
(E) Over the plantar surfaces of the metatarso-phalangeal joints of
all the toes.
I calculate that there are at least fifty-two separate bursæ (about one
hundred on the two sides of the body) in the normal or fully developed
state, though of these many will be found either absent or with very
little of the full structure of a bursa. One small but significant
point may be referred to here. We are all familiar with the prominence
of the knuckles of the hand and the very efficient bursæ which cover
them, but most persons do not recognise that the foot has no such
knuckles (or prominent metatarso-phalangeal joints) and no bursæ over
these joints, except that of the great toe which happens to be very
much more exposed to friction and has a much greater range of action
than the other four metatarso-phalangeal joints. This might be called
by some persons a beautiful bit of adaptation _for_ locomotion and by
others an equally admirable bit of adaptation produced _by_ locomotion.
Examination of Two Still-born Children.
Some further light may be thrown upon the human bursæ by an examination
of two still-born children I dissected in 1908 in Lewisham infirmary,
and give here the results as to the more important subcutaneous bursæ.
_Male Child_: full term.
_Shoulder_: bursæ under acromion processes absent.
_Elbow_: bursæ over outer condyle of humerus present.
" " inner " " absent.
" " olecranon both present.
_Wrist_: bursæ over styloid process of ulna present.
" " " " of radius present.
_Hand_: bursæ over metacarpo-phalangeal joints D 1 absent, D 2, 3,
4, 5 present.
bursæ over phalangeal joints, first set present, second set
absent.
_Hip_: bursæ over anterior superior spine of the ilium both absent.
_Knee_: prepatellar bursæ well-developed.
_Ankle_: bursæ over both malleoli present:
bursæ beneath tendo achillis well-developed.
_Great toe_: plantar bursa present.
_Little toe_: plantar bursa absent.
_Toes_: D 1 (great toe) bursa over metatarso-phalangeal joint
present.
D 2, 3, 4, 5 bursæ over metatarso-phalangeal joints absent.
Bursæ over _Phalangeal joints_.
D 1 present.
D 2, 3, 4, none over either of the phalangeal joints.
D 5 bursa present over the first and absent over the second
phalangeal joint.
This example of a still-born, but otherwise normal infant illustrates
well the previous statement that certain bursæ are congenital and
others of less functional importance are formed after birth. Whereas
the olecranon, wrist, patellar, ankle and tendo achillis bursæ are
fully formed, those under the acromion processes, one of those of the
condyles of the femur, and the digits of the hand, those over the
superior anterior spines of the ilium and those of the foot are little
if at all developed in this case.
Another still-born child at seven months was also dissected and this
had well-formed prepatellar bursæ, scanty ones over the olecranon
processes, also over the small joints of the hand and foot where they
were difficult to isolate and over the malleoli they were only slightly
developed.
A fœtus in spirit I examined and found no commencement of a prepatellar
bursa.
Examination of Living Primates.
_Anthropoid Apes._
Eight of these I examined during life at the London Zoological
Society’s gardens in 1908, four _chimpanzees_, two _orangs_ and two
_gibbons_. These afforded the opportunity of ascertaining by means
of touch the presence, and in a minor degree the size and efficiency
of the main subcutaneous bursa, just as one can do this in a human
subject. The _chimpanzees_ were A, aged thirteen; B, aged seven; C,
aged three; and D, aged two-and-a-half years; the orangs E, aged
thirteen; F, aged three years; the gibbons G and H both two to three
years.
These eight specimens possessed good examples of the leading
subcutaneous bursæ over the olecranon process, the styloid process of
the ulna, the patella and both malleoli.
The smaller and less definite bursæ gave the following results.
_Chimpanzees._
A. _Hand._ Bursæ on all the metacarpal and first phalangeal
joints; none on the second phalangeal joints of D 2, 3,
4, 5.
_Foot._ Bursæ well marked on the five metatarsal first phalangeal
joints; none on D 2, 3, 4, 5 joints, but one on that of D
1. None found on second row of phalangeal joints.
B. Moderate development of bursæ on metacarpo- and
metatarso-phalangeal joints of D 1; doubtful on those of D 2, 3,
4, 5.
On hand and foot first phalangeal joints, bursæ present, on second
row absent.
C and D were similar. Metacarpo- and metatarso-phalangeal joints,
none in C and scanty in D.
No bursæ on any phalangeal joints of hand or foot.
_Orangs._
E. Metacarpo- and metatarso-phalangeal joints, bursæ ill-developed,
first row of phalangeal joints of hand and foot moderate, second
row none.
F. Metacarpo- and metatarso-phalangeal joints more marked than in E.,
and well developed on all phalangeal joints.
_Gibbons._
G. Metacarpo- phalangeal and metatarso-phalangeal joints poorly
developed on D 2, 3, 4, 5, and none on those of D 1. Absent on all
phalangeal joints.
The digits of the gibbons were very long and evidently efficient
in action, but were never flexed to any great degree.
Dead Specimens.
I also examined the hands and feet after death of certain lower
Primates in 1909:--
H. Hapalemur Griseus.
I. Hapale Jacchus.
J. Cercopithecus Callitrichus.
K. Cercopithecus Mona.
L. Macacus Rhoesus.
_Hapalemur Griseus_ H. _Hands._ No bursæ on styloid processes of radius
and ulna, and no localised bursæ on any metacarpo-phalangeal or
phalangeal joints.
_Feet._ Bursæ under tendo achillis small but distinct. Present over
both malleoli.
Metatarso-phalangeal joints D 1, 2, 3, rudimentary D 4 and 5
absent.
First phalangeal joints of D 1, 2, 3, 4, rudimentary absent
over D 5.
Second phalangeal joints absent on all digits.
_Hapale Jacchus_ I.
_Hand._ Lower end of ulna, which is very prominent, a bursa present,
over end of radius, _which is much less prominent_, absent.
Metacarpo-phalangeal joints, present in all.
First phalangeal joints, which are prominent, present in all
digits.
Second phalangeal joints absent in all.
_Foot._ Bursa under tendo achillis and over both malleoli.
Metatarso-phalangeal joints absent on D 1; present on D 2,
3, 4, 5.
First phalangeal joints, present in all.
Second phalangeal joints, absent in all.
_Cercopithecus Callitrichus_ J.
_Hand._ Dorsal surface of the whole hand shows no localised bursæ,
only a loose areolar tissue under the skin. Styloid
processes of radius and ulna no bursæ.
_Foot._ Dorsal surfaces over the whole foot similar to that of the
hand.
Bursæ present over both malleoli.
Well-formed small bursæ under tendo achillis.
_Cercopithecus Mona_ K.
_Hand and Foot._ Dorsal surfaces similar to those of J and similar
loose areolar tissue over styloid processes of ulna and
radius.
Bursæ over both malleoli.
Well-formed bursa under tendo achillis.
_Macacus Rhoesus_ L.
This specimen showed more examples of bursæ than the two
of Cercopithecus.
Bursæ present over styloid processes of ulna and radius,
also over metacarpo-phalangeal joints.
Bursa well-marked over malleoli and under tendo achillis.
Bursæ present over metacarpo-phalangeal and
metatarso-phalangeal joints.
No bursæ over phalangeal joints.
Further Undesigned Experiments.
The preceding facts as to the natural history of bursæ in man and
some lower Primates, even if they stood alone, are enough to produce
conviction as to the manner in which bursæ of all degrees of perfection
are formed by function, and point to the origin of the initial stages
of these structures. But they do not stand alone, for in man there
have been carried out certain undesigned experiments in a similar
direction, comparable to those described in the sections on direction
of hair and arrangement of papillary ridges. These demonstrate the
fact that frequent friction of skin over a hard surface has the power
of producing adventitious bursæ in regions where they are not found in
the normal state.
These adventitious bursæ are the following:--
In the first place certain normal bursæ in important situations are
frequently so much enlarged by the constant irritation of pressure and
friction that they become considerably enlarged. This enlargement may
go on to definite pathological changes and thus come under the care of
surgeons.
They are Prepatellar bursæ--“housemaid’s knee.”
Olecranon bursæ--“student’s elbow” and “miner’s elbow.”
Tuber ischii bursæ--“weaver’s bottom.”
These may be called “occupation-bursæ” and may be classed with three
other well-known adventitious bursæ which are formed on the shoulder
in “deal runners,” on the scalp in “fish porters” and in the back of
the neck in Covent Garden porters, known as a “hummy.” Entirely new
bursæ are formed also over the cuboid bone in talipes equino-varus,
over the internal condyles of the femur in bad cases of knock-knee from
friction of one joint against the other, over the prominent vertebrae
in a humpback. A structure closely resembling a bursa and arising
from similar causes to those producing adventitious bursæ is found in
unreduced dislocations or ununited fractures.
A small example of an adventitious bursa came under my notice. A woman,
E. L., aged 49, had remarkable enlargement of the metatarso-phalangeal
joint of her great toe of the left foot, and over this joint was formed
a well-marked bursa on the dorsal surface. The right foot showed a
much less prominent joint and only a very slight development of the
corresponding bursa.
This instance of a bursa-like structure being produced in unreduced
dislocations and ununited fractures suggests the conception which I
here propose, but do not attempt to verify that _all joints in all
animal forms from the lowest up to man have been evolved in a manner to
which this pathological experiment may give a clue_.
A remarkable case reported by Sir William MacEwen in the Royal
Society’s _Phil. Transactions_, Series B, Vol. 199, pp. 253, 279, is
worth referring to in this connection. It was a case of a growth of
bone in muscle connected with an old injury to the thigh of a man 38
years old, and healthy. At the operation performed by the author of
the paper the tumour was found to be movable, partly attached to the
fascia lata of the thigh, and the upper part of the tumour moved on
the lower. It was found that the tumour consisted of two parts, the
upper three-and-a-half and the lower seven inches long, altogether
a mass about ten inches in length. Muscular bundles of the vastus
externus were included in this ossific formation, one passed through a
tunnel in the bone through which it worked, and the sides of it were
polished. _At the point where the newly formed bone came in contact the
surfaces fitted each other and were polished as if they were covered
with cartilage, and were here surrounded by a capsule._ (Italics not in
original.) This fibrous covering when opened was seen to contain a thin
serum, which, though not of the consistence of synovial fluid, still
aided in lubricating the polished surfaces as they played over one
another.
A similar case was reported also by Dr. C. Paterson, surgeon to the
Glasgow Royal Infirmary.
A very interesting address by the Hunterian Professor, Mr. Jonathan
Hutchinson, was given in February, 1917, on Dupuytren’s work,
especially in the discovery of the cause and treatment of the
contraction of palmar fascia known by his name. Professor Hutchinson
described his method of curing this by the removal of the head of
the first phalanx, and showed excellent results and evidence of the
formation of a perfect new joint to take the place of the old distorted
one, and the fingers were as efficient as in the normal state in the
exercise of flexion. He gives photographs of the hand some months after
the operation showing it to be capable of easy and full extension as
well as of flexion. This again agrees well with the cases of Sir W.
MacEwen and Dr. Paterson of the formation of a functional joint _by_
use and habit.
Another distinguished Hunterian Professor A. Keith, also gave two
lectures in January, 1918, on the “Introduction of the Modern Practice
of Bone-grafting,” which, in its modern form, he assigns to the credit
of Sir William MacEwen. He lays great stress on the important work
performed in such cases by the osteoblasts without whose living and
formative action these results could not be obtained. He explains how
necessary it is that these living elements should be stimulated into
action by _work_. They thrive only so long as they have work to do.
Another surgeon, Ollier, “wondered why the fragments of bone which he
had succeeded in raising from slips of periosteum planted beneath the
scalp or amongst muscles ceased to grow and tended to disappear. These
bony grafts withered because they were not subjected to the strains
and stresses which rouse the activity of osteoblasts.” MacEwen, “by a
fortunate chance, planted his tibial grafts in a situation where they
soon became subjected to muscular strains and stresses. In a short
time bony fragments gathered from the legs of six boys became intrinsic
parts of the humerus of a seventh; from the moment of primary union the
bone cells of the graft were brought under the stimulating impulses of
the biceps and triceps. Osteoblasts are the obedient slaves of muscles;
_muscular dominance is their breath of life_.” (Italics not in the
original.)
“Wolff was the first to devote thirty years of constant work and
observation to prove that the shape and structure of growing bones
and adult bones depend on the stresses and strains to which they are
subjected. By altering the lines of stress the shape of a bone can be
changed.”
Wolff’s law is simply this: “Osteoblasts at all times build and
unbuild, according to the stresses to which they are subjected.”
Professor Keith says further: “We are driven, as I have pointed out in
a previous lecture, to look for the primary cause, not in the bones,
but in the muscles, particularly in those which are tonically and
constantly in action so long as we are standing.”
A terse expression of Wolff’s law is quoted from Dr. John B. Murphy, of
Chicago: “The amount of growth in a bone depends upon the need for it.”
A remarkable illustration of a similar process is given in the
construction of sponges by the scleroblasts and it is stated: “The
soft walls of this sponge are constantly exposed to the force of
moving waters, and we shall see that the spicule-builders--the
scleroblasts--are endowed with the same properties as osteoblasts--the
powers of fashioning and depositing the elements of the skeleton so
that the sponge can best resist the forces to which it is habitually
exposed.”
One more important quotation from this lecture will suffice. “No
one who has watched the behaviour of scleroblasts and marked the
design in their workmanship can doubt that they have acquired certain
characteristic qualities, chief of which is a sensitiveness to
vibrations--to stresses. We see them build the same form of spicules as
their ancestors, and therefore must suppose that their building quality
is a gift of inheritance. We see them alter their mode of building as
stresses change; we must therefore suppose that their inherited powers
can be changed by the circumstances under which they work.”[69]
[69] Hunterian Lecture on “The Introduction of the Modem Practice of
Bone-grafting.” Royal College of Surgeons of England, January, 1918.
Reported in the _Lancet_, February 9th and 16th, 1918.
In regard to the action of the scleroblasts of sponges I have only
to point out that the cautious words of Professor Keith on the
treacherous ground of inheritance amount to the very same conception
of personal selection and inheritance as are involved in the term
“educability” of Sir E. Ray Lankester. Whether or not in the case of
sponges this be a complete account of the matter it at any rate is a
very important piece of evidence, if valid, for selection. Whether or
not further it is a piece of evidence for a Mendelian factor implicit
in the primordial sponges and released by some loss of inhibiting
factors, as Professor Bateson would probably claim, is another and
far more imaginative conception. The mere neo-Lamarckian with the aid
of personal selection fails to see any difficulty in realising the
wonderful process described by Professor Keith.
An apology must be offered here to the patient reader for the
introduction under the heading of the “Evolution of a Bursa” of the
apparently alien subjects of bone-grafts, artificial new joints and
sponge-spicules, but I have hazarded the guess that all joints in all
animals have been fashioned--“forged by the incident of use,” to employ
a fine phrase of Professor Macdonald’s in another connection--in slow
but intelligible ways by use, and that in them, as elsewhere, function
has preceded structure. This arose so simply out of the story of the
bursæ that I ventured to digress as aforesaid rather than make it the
subject of a separate section.
The Significance of the Proceeding.
The foregoing slender contribution to the comparative anatomy and
physiology of bursæ is sufficient to show that at certain important
and “critical” points in the mammalian anatomy, efficient bursæ are
always present. One cannot indeed conceive the function of the parts
involved being carried on at all without these ingenious contrivances,
and no doubt can exist that in certain of the leading bursæ selection
guides and guards, while use and habit maintain them. Over such as
these “dominance” or the appearance of mutations might perhaps be
supposed to preside, and possibly some useful statistical results might
arise from their study from these points of view. But, between these
major bursæ in man and lower Primates and the undifferentiated sacs
which hardly deserve the name of bursæ, there is a perfect little host
of insignificant structures, which at the first attempt at dominion
over them on the part of Mendel or de Vries would hoist the standard
of revolt. These would even refuse allegiance to Personal Selection
under the persuasive banner, “Educability,” which however valuable
elsewhere, must stand aside in this little province of Nature. I have
thus attempted to “Lyell” this body of facts. Basing the statement on
an analysis of a considerable mass of small facts which no one disputes
I claim that the modifications drawn from normal anatomy on the one
hand and on the other adventitious structures, produced by acknowledged
mechanical forces, are examples of the transmission of modifications,
and illustrate the mode of formation of certain initial variations. In
other regions where Plasto-diēthēsis, as I conceive it, is at work in
producing adapted organisms, there may be included in the hyphenated
area certain factors of heredity, Mendelian, mutational and others, but
not in this group. This is merely an assertion of an opinion though I
submit that there is good evidence for it. Not even the hardest hearted
Weismannian, Mendelian or mutationist, and not even the biometrician
can refuse to this poor little province the required time and
mechanical forces, and, unless an opponent can offer some explanation
more consistent with the facts than that here offered, the proof of
causation is as sound as that shown in the larger one of the direction
of hair.
CHAPTER XXI.
THE PLANTAR ARCH.
The principle of Lyell cannot be applied to this section of my
subject for it is unique in the animal world. There is here a simple
compilation of facts such as the medical schoolboy is supposed to know,
and only requires for its setting forth the valuable expert knowledge
of our predecessors in anatomy. It is indeed a pedestrian chapter.
Man alone possesses this mark of a high lineage, and it adds point to
Shakespeare’s description of man as “paragon of animals,” and Huxley’s
“a superb animal, head of the sentient world.” For winning this
integral part of a perfect walking-foot man must stoop to conquer; he
must descend from the trees in order that he may have life and liberty;
whether he bears the ancient surname of Tarsius or the more honoured
one of Pithecus matters not. Names had not in those early times usurped
that tyranny over man’s mind which they have done among his modern
descendants. He came into that terrestrial kingdom which was to be
his own with many a limitation, but with the promise and potency of
an unexampled evolution, when he assumed more fully the erect posture
and saw that his inheritance was very good. Neither then nor since has
he ever reached the fleetness of foot of the Thibetan wild ass, the
astonishing sense of smell of the dog or horse, the keen sight of the
hawk, or the climbing power of that simian family upon whom he turned
his back as on a poor relation. He became _par excellence_ the walking
biped of earth, as, even with greater value to his mastery of the
world he learned to talk in articulate language. A walking animal and
a talking animal, with vast stretches of time for training these new
powers of his, he became modified into the variegated human stocks,
black, yellow and white, that now inhabit the earth.
A Crumbling Arch.
A digression, I hope, will be pardoned here before the value and beauty
of the plantar arch and its mode of forging are described, and it is
possible the latter may add some force to the former. Scientific (or,
must I say?) semi-scientific writings are not concerned with the
snobbishness of much of the pride of birth which still survives among
us. But I would indeed think myself to be doing “my bit” if I could
induce the present generation of young women and men to think highly
of their plantar arches, nobler evidence of a “good” family than soft
fair skin, taper fingers, Grecian nose, slender waist or that hair of
which the decaying line of the long-haired kings of old France were
too proud. For one reason or another, probably analogous to those for
which he has lost so much the vigour of his hair of the scalp, or his
dwindling wisdom-teeth and shrinking little toes, in other words,
racial degeneration, modern man seems to be losing his plantar arch.
For about three years I have made careful but saddening study of the
ankles and feet of young women, and have embodied it in a variety
of journals. This study has included about two thousand examples in
young women of incipient or advanced flat-footedness as revealed,
nay, flaunted before us in our towns and villages. This revelation
has been offered by women’s shortened skirt, so that one can now note
for oneself the ugly and disabling ankles and feet in the streets of
any town, without the complicated business of a surgical examination.
Such an examination, as it happens, and as it is usually undertaken,
serves only to show a moderately advanced degree of this deformity,
indeed, just so much as induces a patient to go to a doctor for relief
of pain or obvious deformity. This is wholly insufficient for the study
of a defect which in the various degrees of its development affects
nearly 90 per cent. of all youngish women so far observed and noted.
The doctors may--or may not--cure this evil, but they are not likely
to find time even to discover during their strenuous lives, the great
spread of this physical defect. But the merciful ukases of fashion,
from Paris or elsewhere, and the obvious benefits, for once, of a
fashion, are so powerful that the short skirt has remained with us for
several years past and does not seem likely to go. I can only hope it
will last until women who lead their sex in these days become ashamed
of the feet of their sisters and their own, and make a forcible attack
upon the Health Minister or Minister of Education, or both, so that
systematic foot-drill in all elementary schools may be established.
No other means than this, added to improved general health, can be
conceived as able to correct so widely spread a deformity. I do not
desire to be considered as making an attack on the bodily charms of
women, for whose multifarious attractions I yield to none in sincere
regard. But here is the revelation, here are the cases walking
unashamed before us, and if the skirts _should_ lengthen again and
cruelly hide up the evil, no one will be induced again to take up the
unpopular attitude of saying that nearly all young women have feet that
are deformed and ugly and, therefore, more or less inefficient. There
is, alas! only too much reason to know that the evil is great among the
better class, even of boys, for in 1919 Captain Coote said publicly at
a Schoolmasters’ Conference that fully 30 per cent. of the new boys
entering leading public schools had flat-foot, and Captain Coote, the
highest exponent of physical training in the Navy, knows a flat-foot
when he sees it. The measures here suggested in connection with the
feet of women have the great merit that from them boys and girls will
alike benefit.
Non-Arboreal Man.
Many problems faced non-arboreal man as he descended from the trees
to claim his suzerainty and place of toil. Not least among them was
the question of methods of protection against the terrible creatures
among which he was to live. Their production must needs be slow, and
for him to meet by “direct action” with weapons invented _ad hoc_
the fierce large carnivora and clumsy but dangerous dinosaurs would
have proved highly dangerous. Too long had they been in possession
of his Canaan, and he could not cross his Jordan, walk seven times
round their Jericho, blowing with trumpets of rams’ horns, and on the
seventh day march in and “consolidate his position.” He had first to
do what his descendants have always been bound to do; he had to learn
to walk terrestrially long before he could think and live imperially.
Sufficient for him was the evil of his day, and, as an old arboreal
denizen he had much to learn and not a little to unlearn; and we know
from the prehistoric pictures of his own doings and trophies, that he
did in course of ages learn to walk, run and jump with variety of step
and efficiency unknown in any other Primate group. We can ask, and we
can but supply speculative answers as to the details of _how_ he did
it, but somewhere and at some time he learned first to become as good a
walking animal as later he became a talking one, and some at any rate
of the steps of the process are plain for all to read to-day.
How the Arch was Built.
Did I not know something of the severity of the judges in such a
Court of Appeal as we are facing in this case and of the opposing
counsel--of the jury I have less fear--I should be disposed to settle
on a half-sheet of note-paper the problem that non-arboreal man settled
ages ago for himself on the ground, by a familiar saying. It really
meets the non-scientific mind which is not weighed down by what Captain
Marryat used to call “top-hamper,” to answer _Solvitur Ambulando_. But
I hear judges and counsel both saying “This will never do,” and must
address myself to opening up the case.
If an adventurous gorilla and his mate, whom we may call gorilla
Columbi, had long ago made a bid for a life completely terrestrial
rather than partly arboreal, it is difficult to imagine how the feet
of this pair could have failed to adjust themselves and their separate
tarsal elements to a better if rudimentary form like that of man, and
that their progeny would not have followed or improved upon this.
Professor Keith,[70] in his work referred to, and Professor Wood Jones
in _Arboreal Man_, have much to say on the evolution of man’s foot
and arch, and I mention this _ab initio_ so as to be free from any
supposed claim to originality which is apt in the present extended
range of scientific progress to be as damaging to a man as for him
to proclaim his honesty or a woman her virtue. And I also formally
grant to the Mendelians and Mutationists, without offence and with
some possible relief to their minds, a period of leave from this poor
trench-warfare--_Plasto-ditēthēsis_ will not be obliged to call in at
the place of its hyphen any reinforcements from these of the higher
command.
[70] _Human Embryology and Morphology._
The assumed precursor of our human walker was probably more highly
evolved in his own special line than the real ancestor, but we have so
little yet of discoveries of whole skeletons of earliest man that the
bodily structure of gorilla C. may fairly be taken as a starting point,
indeed he is for this purpose a valuable lay-figure, almost artistic
for once, on which may be draped the following story of the making of
an arch. The ultimate verdict, which word I use in the old English
sense of a “true saying” rather than the most recent declaration of
those who “ride on white asses and sit in judgment,” does not therefore
invalidate the verisimilitude of this picture. One may go farther and
affirm that, given certain anatomical and physiological facts in an
earlier Primate stock, which marvellously resemble those of modern
man, and it must follow as the night the day that his more primitive
physical basis employed in a new mode of progression, that is of
terrestrial walking on two feet, will be converted by use and habit
into the construction of such new formations as will best agree with
the new style--in other words, in this instance, a plantar arch.
An Unique Phenomenon.
That a plantar arch is peculiar to man is a matter of fact, and
Lydekker in the _Royal Natural History_, Vol. I., p. 41, says of
the gorilla’s foot incidentally “there is no sort of resemblance
to the human instep in the whole foot,” and Professor Keith in the
work referred to “the arch is a human character.” One may see this
for oneself in living apes and monkeys and in the wonderful series
of drawings of apes in all kinds of postures in the _Royal Natural
History_, and indeed in the feet of dead apes and monkeys. All Primates
other than man walk on a flat sole.
Equipment.
Our adventurer starts with the following equipment of tools for making
his arch as he learns to walk entirely on the ground which it must
be remembered he can only do by unlearning _pari passu_ his highly
cultivated power of grasping with his foot. The old and the new cannot
flourish together. The evolving foot of man is an example of a slow
change in the function of an organ and consequent modification of
certain structures in it. He walks with his feet turning in, or in the
axis of the leg; his great toe is not in this axis but may even lie at
a right angle to the foot; he rests weight on his heel and even more on
the outer border of his sole, and thus the sole of one foot turns more
or less towards the other; and he puts a good deal of weight on his
toes which are frequently doubled over; and his gait, though erect, is
never completely so, and is clumsy in appearance.
_Bones_: his heel-bone is relatively long and pointed and slightly
arched below; the bones of his great toe are short and thick, and the
other four toes relatively long and slender. You can see at once it
is not primarily a walking foot. Any active boy of twelve could give
him points and a beating in a race for life in the open. Further, his
foot shows a much larger proportion of the whole foot in front of the
end of the great toe than is ever seen in man. The _ligaments_ which
bind the joints of his foot together, while the muscles play upon them,
are little different from those he will require for the girders of his
arch, except for such a throwing out of slips, and shifting under the
stresses and strains of such walking as his new gait involves.
The _muscles_ of his leg and foot are the most important by far of his
original equipment with which to set about making his arch: he could no
more do this out of his present muscles than a Hebrew could make bricks
without clay. It is these variable and plastic structures which are
most readily adapted by use in a fresh direction or increased degree.
He has the great flexors of the ankle and foot in his poorly-shaped
calf (this feature might be adduced as a human character and studied
in this manner if it were not of so elusive a nature) and the long
flexors of his four outer toes, the special long flexor of the great
toe, which in his case does not of course act in the axis of the other
metatarsal bones. He is lacking here in the special detached portion
of the _flexor accessorius_, which eventually becomes of use in
maintaining the arch, between the heel-bone and the tendons of certain
digits. He has, in a measure, the _oblique adductor_ muscle of the
great toe and the _transverse adductor_ muscle, more for future use
perhaps than of much present value. Like all apes and monkeys he has
a _peroneus longus_ with its tendon passing across the sole from the
outer border to the base of the great toe and a _peroneus brevis_, both
of them for everting the foot and supinating it. But here again he is
lacking, for he has no little _peroneus tertius_, which Professor Keith
speaks of as a muscle “peculiar to man” and “a special evertor of the
foot”--a muscle passing from the tendons of the _extensors_ of the toes
and inserted into the little toe. He has also the _tibialis anticus_
and _tibialis posticus_, the latter which flexes the ankle on the leg,
and the former which also flexes it and everts the foot; he has also
the special _extensors_ of the toes.
This enumeration of the bony, ligamentous, and muscular possessions of
gorilla C. is enough to show that, though he has little of new tools to
make, he has to modify greatly those he has learnt to use so well, so
that one can almost hear him echo the words of David to Saul as to his
new armour.
The problem of an arch remains to be solved by eversion instead of
inversion of the foot, growth in all directions of the heel-bone, and
the enlargement and straightening of the great toe, and the “setting”
of the foot in a certain degree of pronation and over-extension.
Description of the Arch.
The plantar arch is double, but the longitudinal one must be chiefly
considered here. It lies under the concave roof of the tarsal bones,
seven in number, and the metatarsal bones, and rests in a well-formed
foot in front on the heads of the latter, and behind on the inferior
surface of the heel-bone. The _astragalus_ alone of these bones in
contact with those of the leg, acts like a washer to the ankle joint,
and has no muscles attached to it. Three more of the _tarsal_ bones
need reference: these are the three _wedge-shaped_ bones which have
their bases on the dorsal and their apices directed towards the plantar
surface. With such a set of bony tools as this, all the requisites for
an arch are at hand. Let the half-tree, half-ground walker become a
complete ground-walker, and in the first place the manifest increase of
the action of the flexors of the leg will pull to an unusual extent
on the _tendo achillis_ and heel-bone, leading, in accordance with a
well-known law, to steady enlargement of the parts near to which it is
attached. The greater amount of weight thrown henceforth on the heel
tends in just the same direction, indeed, to general enlargement of the
whole bone. The _astragalus_ being in No Man’s Land, so to speak, takes
less part in the change than any other tarsal bone. The _wedge-shaped_
bones are exactly so constructed as to retreat a little in a dorsal
direction as the modified walking increases under the action of certain
muscles which will later be mentioned. This, in conjunction with
the projection backwards of the heel and the general growth of the
bone, permits, as far as the bony parts go, a gradual hollowing out
of the originally flat plantar surface, and the increasing eversion
of the foot places more weight on the front pier of the arch, that
is, the heads of the _metatarsal_ bones. The squeezing-up process of
the smaller _tarsal_ bones contributes also to the formation of the
transverse arch.
The _ligaments_ need no new invention on his part but only a more human
degree of development, and in particular the _calcaneo-navicular_
ligament and _internal lateral_ of the ankle undergo in the human foot
great development, and the long plantar ligament, originally part of
the tendon of the _gastrocnemius_, comes in to the aid of the arch and
goes to bind it together, so that these humbler structures follow in
the wake of the changing and enlarging bones.
The plantar fascia, though a powerful protective armour for the deeper
parts of the sole, cannot be held to enter into the formation of the
arch. The _initiative_ in this process lies with the muscles, and, even
if neither gorilla C. himself, nor his descendants, had altered the
muscles of his foot and just given up climbing for walking, there were
muscles strong enough and appropriate for modifying very profoundly his
simian foot, though he might not have arrived at an arch. He or they
might have become long-distance walkers, but never sprinters.
If the sole of the dissected foot is observed it is seen that the
plantar arch lies approximately over a triangle of which the base is
formed by the _transverse adductor_ muscle of the great toe, across
the heads of the metatarsal bones, and the two sides by the _oblique
adductor_ of the great toe and the _short flexor_ of the little toe. It
extends, of course, somewhat further back under the heel-bone, but this
is its highest part.
In the changing foot the _tibialis posticus_, which was originally a
flexor of the metatarsal bones, obtains a secondary attachment to
the _scaphoid_ bone, and the _tibialis anticus_ becomes inserted anew
into the internal _wedge-shaped_ and metatarsal bones. “Both of these
muscles, thus modified, help to maintain the arch of the foot. So does
the tarsal part of the tendon of the _tibialis posticus_.” (Keith).
The three _peronei_ muscles, especially the new _peroneus tertius_,
attached to the little toe, are called in by increased walking to
redress the balance of forces in the foot and produce that eversion,
with some supination, which is essential to the arch. No arch was
possible till these muscles came into some preponderance of action
over the _flexors_, so beloved of gorilla C. The _short flexor of the
digits_ becomes modified so that its attachment to the tendons of the
_long flexors_ in the sole has its _origin_ completely transferred
to the heel-bone in man (Keith). “It can thus act more powerfully in
maintaining the arch,” and finally the _flexor accessorius_, a muscle
which cannot fail to surprise the dissector when he first penetrates
into the deep layer of muscles of the sole, and which is a detached
piece of the _long flexor of the great-toe_, becomes especially
well-developed and helps to maintain the arch.
The order of events then is: first, increased and altered muscular
function; second, growth of bones and adjustment; third, binding
together of these by new or modified ligaments. If it were possible
to separate in this way the age-long formation of such a living tool
as the human foot, this is the order in which alone, I submit, the
sequence of events can be placed. It is a convenient, because simple
and plain example of initiative in evolution, and I cannot say how much
I owe to Professor Keith’s teaching on the subject.[71]
[71] It is not sufficiently noticed by some writers how important
is Professor Keith’s teaching as to the maintenance of the arch by
muscular action rather than ligamentous union. And it is a very
practical matter from my own point of view in connection with the
prevention of flat-foot in the young. If indeed the poor deformed
feet of the sufferers can only be corrected by attention to the
lowly-organised ligaments, and the muscles will not avail, I can but
add “God help them!”
CHAPTER XXII.
MUSCLES.
A work of great value to the biologist has been written by one whose
work has led him in the widening path of human physiology and its very
title is instinct with meaning. The Integrative action of the Nervous
System may not aid the systematist or the student of genetics, but for
insight into formative powers, where the former can but record facts
and find no interpretation, such a work is of supreme importance.
When the plant sealed its fate and enclosed itself in a cell-wall
and abandoned a life of movement, it was foreordained that its rival
would be that cell and its descendants which could adopt a free
life, and that the future of the world would lie at the proud foot
of that conqueror who could command and mobilize the resources of a
nervous system. And, as we know, it has fallen to man to receive the
rewards of this promise and potency of a higher life. If one seeks to
understand the steps by which man has arrived at his primacy it can
only be by the highway of nervous progress, however much the tracing of
certain connecting or collateral paths may throw light on contributing
causes. So that man’s place in Nature is nearly synonymous with the
structural evolution of his brain, as Huxley has shown in his clear and
simple manner. Even if man is to remain still an animal Melchisedec
for generations to come, or to put it lower, a foundling, no future
discoveries that can be imagined will disprove Huxley’s declaration,
“Evolution is no longer an hypothesis, but an historical fact.” And
yet if man has become adapted to his world, and, in it, crowned with
glory and honour by the unfolding of some original complexity, or as
the result of some fortunate mutations in the distant past, the human
brain, with its cranial capacity of nearly three times the number of
cubic centimetres to that of the gorilla, has been making false claims
to a paramountcy over all factors in the wonderful initiative of fresh
capacities and their mobilisation for conquest. Nothing less than such
a “claim” was understood by the ancients, and, though metaphysics
had to supply the lack of anatomy and physiology, it has always been
held that mind was lord of matter, and now scientific research has
told us why. But no one, even the most hard-shelled scholastic, can
refuse to the brain organ its predominant share in the making of man.
This is seen even in the frigid sphere of science by the difference
of interest there is shown between any great discovery bearing on the
evolution of man, or on some new lower animal form. When Sir. H. H.
Johnston astonished zoologists in 1901 by his discovery and proof
of the existence of an archaic large mammal which had been interned
for an incalculable time in the Semliki Forest, the thrill felt at
that historic meeting passed off very soon when the leading British
biologist had monographed the Okapi, settled its name and surname
and introduced it into text-books. This is never the fate of such
as Pithecanthropus or Eoanthropus dawsoni, or of the more recent
genealogical theory and researches as to arboreal man. The call of
these studies of man’s evolution is felt by all, and the difference in
the two branches of biology may account for what must have struck many
others, that is the neglect of adding the blue ribbon of science to the
honours of the discoverer of the Okapi.
These few trite remarks as to the importance of the nervous system in
the making of man have been introduced here, though they bear more
closely on the next two chapters, because this importance comes in at
every stage of the present treatment of the origin of modifications in
muscle.
Anatomists’ Views of Muscles.
There is a very strict and austere custom among anatomists, which
doubtless is in a measure necessary, of insisting upon following
rigorously the homologies of muscles, especially in human anatomy,
and in this branch of a greater subject the canons are followed to an
extent that surprises the seeker after origins. A remarkable example
of this is in a paper by an eminent anatomist, now Professor at King’s
College, Dr. E. Barclay Smith. It is a paper on the “Morphology of
the short extensor of the human fingers.”[72] He says “the precise
significance of this occasional _extensor brevis digitorum manus_
is a matter of considerable interest.” He gives four possible
interpretations of this unusual muscle. The last, viz., that it is
derived from a new muscle-germ alone interests us here because of the
remarkable caution and austerity of his remarks on this interpretation.
“If an _ext. brevis dig. manus_ cannot be regarded as an atavistic
anomaly, or as a derivative from any existing musculature, the only
way in which its presence can be accounted for is to suppose that
it is of entirely new origin--the product of a new muscle-germ.
Such an explanation is, of course, the last resort, and all other
possible derivations must be disproved before it can be accepted.”
The physiologist would probably think such an interpretation was
the obviously first resort. The same writer discusses at length the
homology of an exceedingly rare anomaly among muscles, the _extensor
ossis metacarpi hallucis_, and his desire on the one hand to find a
missing parent for Japhet, and his honesty and accuracy on the other
hand lead him to say “even when it is present, it cannot be regarded
as directly atavistic, since it does not represent a normal mammalian
tendency.” And he adds a gentle but remote suggestion--“Brooks
certainly describes such a muscle in _menobranchus_ and _hatteria_--two
rare and remote reptiles!” But, lawful and necessary though this be,
there must be stages on the path of human evolution where such a method
must fail and the anatomists can do no more than hold aloof from theory
or speculation, with a certain grim enjoyment of the disputes and
difficulties of the genealogists.
[72] Anatomical Society of Great Britain and Ireland, Trans., p. 54.
Initiative in Muscles.
Initiative in the evolution of muscles clearly occurs somewhere in
the stem, and behind the formed expression of an altered habit is the
integrating action of the nervous system. This will be by some looked
at askance as a _deus ex machinâ_ and reckoned as part of the argument
from ignorance in a way which recalls Weismann’s scorn of Lamarckian
factors in germinal selection. I submit that what he and Osborn call
“the unknown factor” of use and habit, arising in response to new
stimuli meets as no other proposed suggestion does the formation of
new muscles. Given a certain fundamental architecture of skeleton and
musculature, such as of primitive vertebrates, one can, without doing
violence to any known facts, place the formation of new organs of
movement in the following order:--
1. Neural changes and habits.
2. Muscular modifications.
3. Consequent modifications of bone. It carries the question no further
to say that these are correlated, however loose may be the meaning
of that word that is understood. If the prerogatives of Selection
within the germ, of segregation of unit-characters and dominance,
and of mutations are not unlimited in the construction of organisms,
there still remains a sphere of action for the initiating power of
the nervous system. Bones grow and change their form in response to
increased or altered muscular action on them, and it is necessary to
look back a stage further in the story to the neural changes however
produced. There have been abundant opportunities in the long history
of mammalian evolution for primitive forms to take a new course of
life, and they have done so on an extensive scale. The impulses that
have led them may have been started by some “needs” such as Lamarck
taught, some change in their surroundings involving new stimuli, or
“insults,” as Haeckel called them, but the first of the structural
stages must have been in the cerebral cortex.
Cross-Roads in Evolution.
The most instructive levels of animal evolution are those where two or
more great stocks have diverged from a primitive one. There may have
been several factors leading to the division of the early Ungulates
into the odd-toed and even-toed groups, of the Carnivora into cats,
dogs and bears, the Felidæ into the highly-specialised genera of that
intense family, the early parting of gibbons from the common anthropoid
stem, and then the division of this line into the three great genera
with which we are familiar. Whatever may have been the unknown factors
in the environment such as changes of climate and level, geographical
isolation, increase of foes, profusion or lack of food, to which these
diverging stocks became adapted in their organs and form, in fact
whatever we do _not_ know, we know this--that in their measure they
acquired more convoluted and often larger brains, and the stimuli
passing through their receptors into their consciousness increased
with an everflowing tide, in volume, intensity and complexity. Many an
archaic habit of their race they must unlearn, and it is doubtful if
germinal selection would avail in this valuable process of economy as
it is held to do in the case of the human little toe.
It may be taken as granted that increasing complexity of brain in their
own lines of life did accompany these adventurers of small or large
groups. It follows that muscular changes from the original stock would
follow neural changes, for movement and activity is inseparable from
the animal, and the integrating action of the nervous system would
constantly initiate, maintain and establish fresh habits and these
be expressed in new muscular structure. Whatever higher uses, as we
believe them to be, man makes of his brain, as reflection, reasoning,
imagination and association, such were not the new properties acquired
by these adventurers. They were very much concerned with hunger and
love, and for them “philosophy” did not sustain the structure of
their world. But more varied movements of head, trunk and limbs, and
greater agility and strength brought them such prizes as were within
their reach. This may be only another way of expressing Sir E. Ray
Lankester’s conception of educability, which he maintains to be the
only acquired character the organism inherits, and it may be therefore
assumed to be under the iron law of selection. This must be accepted
with the respect due to the high authority from which it proceeds. But
such a conception, while it removes a false light in certain regions,
sheds no light on the pathway of animal evolution, unless modifications
be transmitted, and we can now take it that man does not inherit the
power to speak which for incalculable ages he has been learning,
nor to write, even though in the days of the early Pyramid-builders
and the Sumerians in the plains of Chaldea they possessed the power
of writing, nor can a musician’s child learn to play an instrument
without teaching, or indeed man perform any of his arts and crafts by
second nature: so, negatively, this knowledge is valuable, and the
neo-Lamarckian must proceed on his quest without anything more than
educability to aid him--but it will serve. The fact is that we do not
inherit habits or associations as such at all, but the neurones of
the grey matter in spine and brain which subserve, direct and control
them. Though a fresh neurone or two in the brain of an early ungulate
deliberating, so to speak, as to the life he shall take up, whether
that of oxen or horses, may be trifling in itself as to immediate value
to the animal, it may be to him as much a matter of fate to acquire
those microscopic cells as it was to the undifferentiated organism
that paused before it sealed its fate as plant. Under the free and
enlightened government of the integrating nervous system liberty to
express itself to an almost unlimited extent, in accordance with
progress, is thus open to the hypothetical adventurers.
When considering such an aspect of the organism as the “choice”
between the career of an odd-toed or even-toed ungulate, a cat or
dog, a lion or tiger, a gibbon or other of the four anthropoid genera
which assuredly was presented to certain groups of primitive ungulates
carnivores, felidæ or apes, as historical beings, the vision of the
process is sore let and hindered by the limiting force of certain
expressions which have been sanctioned with the _imprimatur_ of fifty
years’ high thinking in the realms of high biology. I refer of course
to the terms Selection and Evolution which, though they cannot be
replaced by better terms, have the power and sometimes have had the
effect of impressing on the story of organic existence an aspect of
_determinism_ which does not allow, for any purposive action of the
individual, the working out of its own salvation, on the part of higher
forms at any rate. As among nations self-expression has become of late
a powerful force in their development, and indeed of individuals, so
it may be argued by analogy that the total experience of an organism,
may result in its co-operation in the process of its progress towards
higher things. Bergson hints at such a process in organisms, but
appears to allow nothing for the individual in his _élan vital_, where
the mass alone counts. So if the two binding terms of Selection and
Evolution must be granted their enormous power over our thoughts, there
must be also a loosing as well as a binding, and we, as well as certain
young ecclesiastics in a hurry, may put in a plea for Life and Liberty.
Thus is Lamarckism immortal, and the integrative action of the nervous
system supplies the reason.
This well-worn subject is not out of place here, where I am trying to
show evidence of self-expression in terms of muscular modification
arising from fresh activities of the brain.
New Muscles.
If it can be said without fear of question that “the differentiation
of muscle and nerve is the morphological result of division of labour,
whereby the unit of protoplasm, in which irritability and contractility
are combined, has, on the one hand, become modified into muscle, which
retains the property of contractility, and on the other into nerve,
which retains that of irritability,”[73] and if Wolff’s _Law of Bone
Transformation_ teaches that if a normal bone is used in a new way its
structure and form will change to meet its new function, which Sir
Charles Bell had more vaguely taught in 1834, it cannot well be denied
that at certain turning-points in the history of animal organisms the
sequence of changes which arise is neural change, muscular modification
and finally change of bone, whether ungulates, carnivores, felidæ,
gibbons or big anthropoids or man, be the _dramatis personæ_. The only
question is whether selection or use and habit initiates the subtle and
slow process.
[73] Macalister, _op. cit._, p. 62.
Unstriped Muscles.
The simplest of the muscular acquirements of mammals is of course
that great mass of little structures which constitutes the unstriped
musculature. I must admit that here again I am engaged with what the
professed biologist may call trifles, but these, like some others of
a corresponding rank, have a provoking quality of persistence, and
display, if one may personify them, an insistent desire to know whence
they come and why they are here. Some of these, like the one before
us, may be comprehended in the great chapter of the Evolution of the
Indifferent of which they form a page. This world, at any rate in the
moral sphere, would be an intolerable house of bondage if there were
not many _things that matter not_ as well as _things that matter_, and
there is reason to believe that in the process of the making of man and
a vast number of forms below him there is a large field of structures,
parts and organs, where things that matter not are to be found. One
strange province of this realm is the colouration of animals in certain
regions where no eye ever can see the colour or can take any heed of
the markings, treated very fully many years ago by Mr. Beddard in
_Animal Colouration_.
Unstriped muscle arises, as the striped variety does, from the
mesoblastic muscle-plate and appears in nearly all organs,
blood-vessels and skin, and as trade is said to follow the flag, so
a development of new unstriped muscles must speedily be found in
every new structure of the regions where unstriped muscle is found.
The skin is the simplest, and less complicated by the presence of
other structures than vessels and organs, where it also exists, but
where it trespasses too much on the territory of selection for my
immediate purpose. A small band of this muscle called an _arrector_,
or _erector_, _pili_ is attached to most, if not all, of the third of
a million hairs which cover the skin of man, and is inserted into that
side of each hair which forms an obtuse angle with the plane of the
skin. This tiny structure is endowed with the quality of contracting
in response to certain stimuli falling on the skin, so that it causes
the hair to which it is attached to stand erect instead of sloping, and
incidentally squeezes some of the secretion out of the sebaceous gland
which lies in each angle. The human skin thus possesses about a third
of a million minute muscular bands and shows no sign of parting with
this old gift from a lower hairy stock, and whatever value, if any,
their function be to their possessor they show a remarkable readiness
to perform it efficiently. It makes their existence and persistence no
clearer to call them vestigial, for one only thus throws the question
of their origin much farther back. Undoubtedly they come from afar
and were in full development in the earliest hair-clad mammals, so an
ancestry reaching back to Monotremes or Marsupials is not to be lightly
set aside. The raw material was undoubtedly formed in response to
stimuli conveyed to the brain, and the earliest appearance of muscles
which erected the hairs must have been wholly insignificant either upon
the survival or comfort of the possessors.
A Remarkable Example.
The _arrectores pili_ exhibit very little evidence of control or
interference from the action of the brain, but there is one region of
one animal, like the Rosetta stone that set Champollion at work, where
a very simple hieroglyph is recorded. I have been able to find no other
in all the hairy mammals I have examined than that startling pattern
which the back of the lion, shown in Fig. 37, sometimes displays. That
well-formed patch of reversed hair of roughly triangular shape which
is frequently found on the back of a lion has been described and, as
I interpret this strange structure, it would seem clear that neural
change in some examples of this species has led to so persistent
contraction of the _arrectores pilorum_ over a certain area of skin,
and that these have permanently reversed the normal and primitive slope
of the hair. I have never found it present in a lioness, and not in
all cases of male lions. It marks its possessor with the brand of a
fierce and especially savage character, and he is not able to screen
it from the eye of the Zoologist as well as Milady did her brand of
shame, until that fatal day when D’Artagnan disclosed it. This pattern
on a lion’s back is strangely reminiscent of the ridge of bristling
hair we see on the corresponding region of a fierce dog’s back when he
is infuriated. In the latter it may be said to have selective value,
as perhaps also is the bristling hair on the head of a gorilla when
enraged, much in the same way as the Chinese warriors sought to alarm
their enemies by terrifying grimaces, or those terrifying tones and
expressions of face which the Tyrant man, really a coward, is said by
such as Miss Wisk to exercise over the women of his circle. We may
present all these to the Pan-Selectionist, but inasmuch as the short,
bristling hairs on the back of a lion are on the one hand hidden by
the mane from an animal in front, and on the other are so small as
to be seen quite close if at all, the survival-value of the reversed
pattern of hair in question is quite outside the province of selection.
It is so manifestly under the control of cerebral action, that it may
be compared, as an undesigned experiment, with that of man in placing
harness upon a horse, as to the power of cerebral action in producing
structure. Though, as far as I can learn, it stands alone, it is
difficult to believe that such a thing as a unique example occurs in
nature, but it is interesting and suggestive from the Lamarckian point
of view, and even the opposing counsel must admit that it is among
indifferent structures.
Facial Muscles of Expression.
This record in terms of hair of personal and ancestral emotions has,
however, a link with certain more numerous and important striated
muscles, such as the facial muscles of man and apes, modifications of
the great platysma-sheet, and which are disposed in two layers, a deep
and a superficial. This covers like a hood at the third month the head
and neck of the embryo, and later assumes on the face its specialised
form of certain bands which operate round the eyes and mouth. As they
are of the striated kind these muscles can be moved at will, but their
main action is much more under the government of the mental processes
of their possessor. As they are fundamentally the same in apes and man
very little new muscular structure arises in man, and little more than
shaping or refining takes place.
The facial muscles which operate round the orbit have less mental
action represented in them than those of the mouth, though the action
of the special elevator of the upper eyelid is conspicuous among the
expressions of a vigorous person. Both apes and man have muscles on
each side which raise or lower the angles of the mouth, draw the
angles upwards and outwards, and raise the upper and depress the
lower lip; and, though the muscle of the mouth which corresponds
to the _orbicularis_ of the eye is not a continuous structure, but
formed of interrupted bundles of fibres, it is powerful in closing the
lips and active in the expressions. There are also in man scattered
oblique fibres in the substance of the lower lip, well-developed and
closely-set in a sucking child, and these in the adult are scattered
and less conspicuous.
There is thus a remarkable set of structures in the face of a higher
primate which convey mental emotion. As they also belong to animals
with a high degree of convolution of brain, though certain are found
in lower mammals, their specialisation is only to be accounted for by
the long-continued involuntary expression of mental states existing
in the particular form of primate. Professor Keith says in the work
before referred to: “Muscles supplied by the facial nerve are the
physical basis into which many mental states are reflected, and in
which they are realised. Through them mental conditions are manifested.
It is found that the differentiation of this sheet into well-marked
and separate muscles proceeds _pari passu_ with the development of the
brain. The more highly convoluted the brain of any primate the more
highly specialised are its facial muscles,”[74] and he points out in
a smaller work[75] that in the gibbon, and monkeys of the Old and New
Worlds the facial system becomes simpler and at the same time more
robust, and he pictures the facial muscles as the “servants of the
brain.”
[74] _Embryology._
[75] _The Human Body._
If an ape can express a good many of the coarser emotions of an animal
by the action of its facial muscles, and through kindness and training
exhibit some of the finer ones, there is a wide distance between this
level of attainment and the multiplied moods and unnumbered varieties
of expression which give to the human face its unique charm. If we can
express pleasure, pain, anger, contempt, hatred, surprise, affection,
sympathy, fear, hope, reflection, perplexity, gaiety, melancholy,
cunning (and many another can be supplied) what a remarkable field of
physiology in terms of anatomy we have in the facial muscles! There is
a very obvious reason why none of these emotions have been fixed in an
objective form in ape or man, as the patch of reversed hair is on the
back of a lion, for moods and states of feeling in every individual man
are subject to such endless variations that it would be impossible for
them to stamp any individual face with a record of even one emotion
which could be transmitted to descendants, to say nothing of the
inconceivably great probability that heredity would at once swamp any
initial modification.
Three Stages.
The stages then are but three--mental states, specialisation of small
muscular bundles from an existing simple sheet of muscle, and disuse
of the remaining portions, and in this small but highly significant
field we see structures created independently of will as servants of
the brain, and without any survival-value in their earliest stages.
It is more than likely no monkey, ape, or early man whose face was
covered with thick hair from his eyes downwards, ever saved his life
or gained a better mate by reason of the subtle modification of a tiny
muscle which was proceeding _pari passu_ with the growing complexity
of his convolutions and their manifested emotions. This is not to
claim that a more modern man or woman would not find sexual selection
of value by reason of his or her more pleasing or commanding facial
expression. That the initiative of these alluring modifications was
simple and Lamarckian cannot be gainsaid, whatever the fruit of the
finished process may be to-day. We know in our own experience that many
a handsome person with good features and little expression is often
unsuccessful in the matrimonial market, when another with defective
features and a fine, delicate, attractive expression takes the prize.
So the early story of the formation of muscles of expression is seen to
be a page in the evolution of the indifferent.
The Fly-shaker Muscle.
The panniculus carnosus, of which the facial muscles are part, is a
great system of musculature found in various animal forms, and it
furnishes a field for study of the evolution of the indifferent and the
initial stages of the formation of a muscle. This is a servant of the
brain in a more indirect manner than the facial muscles, but it, too,
arises in obedience to the integrative action of the brain. The early
specialisation of it need not be considered here. It may be considered
unwarrantable to claim the great Fly-shaker muscle of Ungulates as an
indifferent structure, but the arguments by which the Pan-Selectionist
would annex it to his sceptre, as a triumph of the minute care of the
organism by selection, rest only on the assumption that he knows how
it has become an adaptation to the life of its possessors. This is
now more than it used to be a matter of opinion since the publication
of Professor Bateson’s revolutionary _Materials_, and others beside
he have reserved to themselves the liberty of doubting the accepted
explanations by the tangled path of adaptation. The statement of
Weismann, “Everything is adapted in animated nature” was necessary
to his theory of germinal selection, but it admits of extensive and
numerous exceptions in view of the fact that so much of adaptation is
partial and imperfect. If he had said that _every organism_ as a being
is adapted he would have been nearer the truth, but that every tissue
and part of an organism is adapted is demonstrably untrue. A large
number of organisms, themselves apparently well adapted, flourish well
enough and reproduce their kind in spite of faulty and rudimentary
tissues and parts. If it were not so we should have seen little of
progress except what come under the laws of genetics,--a distributional
matter. Even the super-Geddes could not distribute what was not there,
for he could not deal with raw materials and change them by a fairy
wand into manufactured articles. In the great field of domesticated
plants and animals man has to find not only some mutation or some
dominant strain and breed it to his will, but to cultivate the domestic
qualities of animals and employ cultural conditions for plants. There
is doubt expressed as to the length of time or numbers of generations
during which these cultural conditions can extend, but Professor
Thiselton Dyer many years ago made the remarkable statement as to
plants:--“While specific stability under constant conditions appears
to be the rule in nature, it is widely different in cultivation. When
a plant is brought under cultural conditions it maintains its type for
some time unaltered, then gives way and becomes practically plastic.
From my experience at Kew, where I saw the process continually going
on, I hazarded the generalisation that any species, annually reproduced
from seed, could be broken down in five years. During that period
specific stability, though menaced, tends to maintain itself. Darwin
was well aware of this.”[76]
[76] _Nature_, November 28th, 1907, p. 78.
Most biologists from time to time betray the fact that their minds can
only be relieved from an intolerable burden, in accounting for the
numberless adaptations in organisms, by the view that many of them
originate through factors of use and stimuli from environment, and
at first are entirely indifferent as regards the survival or better
mating of their possessors. To which the stern opponent replies, “What
is there to show that in the existing scheme of things there is any
provision made which will minister relief to the burden of your little
mind?” To which, “answer came there none,” except a subdued reflection
that everything we see of living, striving nature around us has a
most provoking way of speaking to us of daily, hourly and incessant
action and reaction, stimulus and response, and that those who view the
process thus do seem to bring some order into what would otherwise be
chaos--and yet all the while someone is being grossly deceived! This
“may be magnificent but it is not proof,” some will say, and will ask
if the older observers of the heavenly bodies were not wrong in their
complete conviction that the sun went round the earth. This digression
introduces the role of the fly-shaker. If I am told that this muscular
sheet in a cow or horse to-day is a relic of raw material inherited
from a remote ungulate stock little evolved, and that it contributes in
hot weather in the time of flies to the comfort and better mental state
of the cow or horse, that it shall be able to keep those enemies at
bay, and that the muscle is kept well in order by two or three months’
practice in each year I can understand in a measure its presence
to-day. It has an efficient ally in the sweeping tail of a cow and
that of a wild horse, and both of these weapons are further aided by
the mobile ears of cow and horse, and the stretching movements of its
head and neck. Thus the body of a cow, for example, is like a map with
four territories delimited, that of the fly-shaker, the tail, the ears
and the head and neck. Between these offensive weapons a cow is better
defended against flies than a European in India by his punkah, or China
was by its great wall, or Britain by the wall of _Vallum_ of Hadrian
or the wall of Severus, which with forts and garrisons was designed
to protect it. Speaking in allegory the evolving brain of an early
ungulate occupies the position of an ancient Chinese Emperor or a Roman
Proconsul in Britain in its provision against “barbarians,” either
Asiatic or Celtic. The resemblance goes further, for no experienced
Roman General, whatever the Celestial minds in China may have thought,
would fear that the loss of a sector of his wall would imperil the army
of occupation in Britain or the fabric of the Roman Empire. But as, in
the long run it contributes to one’s welfare to be comfortable, and
even the domestic ungulate is somewhat of a hedonist, a well-developed
fly-shaker is maintained, the occasional use of which in winter and
frequent use in summer and the active purposeful switching of tail,
twitching of ears and jerking of head have their limited value. Here
there is ample room for diverse opinion and the opponent will ask
with some degree of force how we know that there is no more benefit
to the cow from its fly-shaker than a mild degree of comfort, and may
assert that the possession and use of it may have survival-value by its
defence against deadly parasites. We do not know, nor does he, but it
would seem that except for the tsetse fly in Africa the plague of flies
does little to an ungulate beyond irritating its brain, and if he had
no fly-shaker, he would still be able to reach a considerable distance
with his tail, ears and head over the irritated regions. The question
of survival indeed resolves itself into the vigour and energy of his
integrating brain.
To this view of the function and origin of the panniculus carnosus the
busy systematist and student of genetics may refuse to listen, and pass
to the order of the day, but I submit that in stating a position it is
useful to put forward a crude example in which the issue is plain, and
which subsumes an immense number of smaller and more subtle cases, and
in a region where the most hardy rebel will not dispute altogether the
sway of _personal_ selection. It is a question here of the manner in
which, speaking in metaphor, the early ungulate first set about making
his eolithic or palæolithic weapons and fashioned them into what we see
to-day. “Forged by the incident of use” and habit meets the story of
the fly-shaker far better than some mutation arising in far back ages
or some dominant variation, or “useful variation within the germ.” At
any rate Lamarck finds the raw material to hand, and there are supplied
adequate noci-cipient stimuli with response, in regions where these are
most active under the dominating action of the brain.
Other Muscles.
In the skeletal muscles of the primates many muscles offer themselves
for consideration as examples of inherited structures arising under
the stimuli of altered function, and only a few of these will be dealt
with. It might appear sufficient to those who yield, perhaps too
willingly, to authority, if I were here to try and prove my point by
quoting the statements of one of the greatest anatomists of our time
and country, and so pass on--but it is to be feared authority cannot
carry one far in a dispute so important. Macalister says, however, “The
anatomical arrangement of the muscular system is the physical exponent
of habitual actions and those actions are the chief factors in moulding
the bones and in regulating the position of the somato-pleural vessels
and nerves”--and “the locomotory function and consequent utility of the
trunk-muscles were lost when the early vertebrates became terrestrial.
In higher vertebrates, and notably in man, the mobility of several
regions of the vertebral column differs both in degree and kind: the
outgrowing vertebrate processes show consequent variations, and _the
muscular system is varied accordingly_.”[77] Also “as both origins
and insertions (of muscles) are the creatures of habit, they are both
equally variable with variation of function; but, as in higher animals
the kind of work to be done is more constant than its degree, so,
as a rule, insertions alter less than origins.”[78] Macalister, at
any rate, held a very clear dynamical rather than static view of the
making of the muscular system. But as the days of authority are in a
certain sense gone for ever, and we live under the reign of experiment,
research and questioning, every biologist, within certain limits, does
what is right in his own eyes; there is no King in these days.
[77] _Op. cit._, p. 71. (Italics not in original.)
[78] _Op. cit._, p. 73.
Skeletal muscles are structures in which, if ever, the factors of use
and habit and disuse would be shown, because muscle is a tissue, with
highly active metabolism, so that it has been called “an expensive
tissue” for the animal to maintain.
Muscles of Primates.
This physiological fact agrees with the anatomical results of an
extended study in the musculature of primates, especially of man, and
Hartmann’s book on Anthropoid Apes supplies abundant evidence of the
variations of the muscles of these animals, which are not at all more
striking than their differing modes of life would suggest. It would be
wearisome to quote all these, but a single muscle may be given as an
example of a special ape’s muscle with variable distribution. It is
called _latissimo-condyloideus_ and starts from the insertion of the
_latissimus dorsi_ and passes along the inner aspect of the humerus
for a variable distance. In the _baboon_ and others it goes to be
inserted into the inner inter-muscular septum and the internal condyle
of the humerus, in the _orang_ to the condyle, and in the _gibbon_ to
the centre of the shaft. As to origin it proceeds from the insertion of
the _latissimus dorsi_, but in the _gorilla_ from the coracoid process
of the scapula and from two portions of the _pectoralis minor_, and is
finally attached to the inter-muscular septum between the _brachialis
anticus_ and the _triceps_; in the _chimpanzee_ it divides into an
anterior and posterior portion, the former being attached to the inner
condyle, the latter to the middle and inner head of the _triceps_;
in the _orang_ it divides similarly, but in one particular example
it had an anterior thin portion attached by a slender tendon to the
coracoid process of the scapula and a posterior portion arose from the
_latissimus dorsi_; in the _white-handed gibbon_ it arose from the
function of tendons from the _latissimus dorsi_ and _teres major_ and
was inserted into the fascia between the tendon of the _biceps_ and the
_brachialis anticus_.
Such a divergence as this within the strict limits of an anthropoid
muscle, concerned in the various forms of climbing action of these
apes, can only suggest an origin from a divergent set of functions and
small details in their respective modes of climbing.
Hand and Foot of Man.
Both the hand and foot of man supply a small muscle for consideration
in the present connection of habit with formation of new structure.
If man be regarded as of simian origin there are not as many entirely
new muscles in his equipment as would be expected from his departure
from the habits of simian ancestors, though many muscles are found to
be altered in size and shifted from the ancestral positions. But the
human hand presents one suggestive example of a little muscle not found
in any other animal, the special small extensor of the thumb, arising
from the interosseous membrane between the radius and ulna, and from
the radius, being segmented off from the _extensor of the metacarpal of
the thumb_, and it accompanies this muscle and tendon to be inserted
into the first phalanx of the thumb, and is peculiar to man. It can be
easily seen at the radial border of the well-known “snuff-box” which is
produced by it when it is fully extended. This is of course a muscle of
small importance to the functions of the hand, and its appearance in
man can only be supposed to be a subordinate detail easily derived from
the _greater extensor_ by reason of the more delicate adjustment to
complicated movements of the hand under the directing power of higher
cerebral development.
Peroneus Tertius.
The foot of man possesses the small _peroneus tertius_ which was
referred to as one of the evertors of the foot concerned in the
construction of his plantar arch. Macalister and Professor Keith both
speak of it as peculiar to man, and the latter refers to it at some
length,[79] the whole passage being worth quoting here. “Although
the evolution of the human method of progression was attended by a
profound alteration in the form and action of every muscle and bone
with lower limbs, yet this great transformation was produced without
the appearance of any really new element. One new muscle--the _peroneus
tertius_--did appear, and the history of its evolution throws an
interesting sidelight on the origin of new structures. It arises by
the outer fibres of the common extensor muscles of the toes being
separated. In all the anthropoids the feet are so articulated at the
ankle-joints that the soles are directed towards each other, and only
the outer edge of the foot comes to rest on the ground when the animal
tries to stand. The feet have a tendency to assume a similar position
in children at birth. The advantage of a muscle, such as the _peroneus
tertius_, is apparent in the human foot, for it tends to raise the
outer border of the foot, so that the sole is properly applied to the
ground. If we examine the muscles which, rising from the front of
the leg, cross the ankle-joint to end on the back of the foot on the
toes of fifty men, we shall find every stage in the evolution of this
muscle. In one man at least it will be undeveloped; in two or perhaps
three it will be represented by a part of the tendon of the extensor
muscle of the little toe, which in place of ending entirely on the
toe sends a part to end on the metatarsal bone of the little toe. In
only forty of the fifty men will the _peroneus tertius_ be found quite
isolated from the parent muscle--_the extensor communis digitorum_, and
to have a distinct origin from the fibula in the leg, and a separate
insertion to the base of the fifth metatarsal bone in the foot. In a
series of fifty specimens every stage in the isolation of this new
muscle will be seen. It has never been found in any anthropoid, and is
more often absent or undeveloped in African than European races.”
[79] _The Human Body_, p. 92.
To this excellent account I have only to add one comment. It can
hardly be an accident or without significance that this special human
evertor of the foot concerned in the construction of the plantar arch
is “often absent or undeveloped” in African races, which are well-known
in some groups to have adapted themselves to a form of foot which shows
no plantar arch, being normally flat-footed. In this small field of
observation, a mere plot of lentils like that which Shammah defended of
old, there is set forth a mimic battlefield, and it is not difficult
to see that the forces at work can owe allegiance to one and one only
of various commanders. The problem as to the origin of the _peroneus
tertius_ would no more attract the Mendelian than did the trousseau
and approaching marriage of Caddie Jellyby attract the far-away gaze
of her mother, fixed upon the world of Borria-boula-gha, and, for that
matter, de Vries would hardly pay it more attention--to him it would
be indifferent; whereas Weismann would have as much to say about it
as about the little toe of man, which furnished for him and Herbert
Spencer such fruitful material for debate many years ago. This muscle
resembles the results of some of Michael Angelo’s first attempts at
sculpture, thrown aside perhaps in his place of work and from time to
time taken up, rough-hewn again and again and finally shaped into a
form far from perfect, but with the value and teaching of a failure
for him who was some day to outshine all modern rivals. If the history
of this muscle be not one of initiative in evolution through the
factor of use and habit the Pan-Selectionist must do the best he can
with an incalculable number of “trials and errors,” and must suppose
that, rather than allow this small territory to the neo-Lamarckian, a
long series of man’s ancestors have been making experiments for the
benefit of man’s walking power under the guidance of selection with
an insignificant muscle whose only function is that of aiding in the
eversion of the foot, and that in the rudimentary condition described
by Professor Keith it had selective value. No one who was not committed
to a dominating theory could hesitate for a moment which of the two
alternative views of the origin of the _peroneus tertius_ he would
choose. Dr. Barclay Smith speaks in the paper referred to above of the
_extensor brevis pollicis_, or _minor_, as a muscle of extremely late
appearance, and as “peculiarly human,” and says all the evidence points
to its being a segmentation product of the _extensor ossis metacarpi
pollicis_, its appearance being foreshadowed in the anthropoid by an
extension of that muscle on to the proximal phalanx of the thumb.
It is not without interest to the thesis before us to read the rather
bewildering story of the early life of a very insignificant muscle such
as the small extensor of the thumb of man.
As illustrations of the moulding and pruning of perfected muscles it
may be remembered that, as Macalister says, “portions of muscles may
also become detached and degenerated so as to act as ligaments,” and
“the adult muscular system of man bears everywhere traces of earlier
cleavings and subsequent fusions, partial disappearances and local
outgrowths.”[80] This passage recalls one in which Huxley says in
watching certain phases of development you can almost see the hidden
artist at work, and here the sculptor may be pictured in his chipping,
trimming, rejecting and finally shaping, some creation of his brain;
and from a biological point of view a vision of the processes of use
and disuse may be obtained. Professor Keith also speaks often of the
migrations of muscular attachments in a way which agrees with the
passage quoted from Macalister.
[80] _Op. cit._, p. 73
CHAPTER XXIII.
INNERVATION OF THE HUMAN SKIN.
For at least seventy years the surface of the human skin has been
the subject of so much physiological observation and experiment that
Professor Sherrington considers the literature connected with it to
be probably greater than in any other branch of physiology. Most of
this study centres round the skin as a receptive field and problems of
the nervous system. It is easy to see why this should be in the case
of an organ so great as the skin, covering all the other structures
and organs and exposed through ages of evolution to the vicissitudes
of an inconceivable number of stimuli. And one outcome of this study
is to show that, metaphorically speaking, the skin is a mosaic, and
not the confused and blurred production of a child of four years old
who has been given a sheet of paper and a paint-box. There is order
in this field, and even without calling in final causes, plan and
purpose. Beside the protective function exercised by the skin it plays
a large part, through its nervous endowment, in the processes by which
the brain is made aware of the surrounding phenomena, thus conveying
intelligence to the centre of life only less important than that of the
special senses. It is maintained here that the result of the various
physical stimuli, of which pain, cold, warmth and touch are the chief,
is that certain functions and structures of the skin have arisen in
response to them.
This is, no doubt, to beg the question of origin, and if the balance of
evidence be seen to be against this view the order of events would need
to be stated differently. But the position is clear, whether correct
or not, and if it be shown to be erroneous it will at least have good
“lighthouse value.”
Observed Facts.
Briefly stated the facts of the innervation of the skin are of two
orders, anatomical and physiological; the former examined by the aid
of the microscope, the latter by physiological experiments of a varied
kind. The chief aspect in which these are viewed here is the mode of
distribution of these two groups of fact, and it is held that this
strongly suggests without proving it, the alleged mode of origin of
both.
TABLE I.--_Distribution of Touch Corpuscles_:--
In the deep connective tissue of the dermis there are:--
In the thumb about 70.
" " index finger 105.
" " middle finger 60.
" " whole hand 500.
They are numerous over finger joints and front of elbow joint.
In all 530 about the joints of the upper extremity.
317 about those of the lower extremity.
TABLE II.--(_From Schäfer’s Text Book of Physiology_):--
Average of Meissner’s corpuscles to each square millimetre, which is
approximately one five hundredth part of a square inch:--
Palmar surface of distal phalanx of index finger 21
Palmar surface of second phalanx of index finger 8
Palmar surface of first phalanx of index finger 4
Palmar surface of metacarpus of little finger 2
Plantar surface of distal phalanx of great toe 7
Middle of sole of foot 2
Flexor surface of forearm in each sq. mm. 1
Distal end of flexor surface of forearm in each sq. mm.:--
1 to each 6 sq. mm. approximately.
* Absent from the cornea, and conjunctiva of the upper eyelid and
from the glans penis.
TABLE III.--_Distribution of Touch Spots_:--
These must be distinguished, of course, from the touch _corpuscles_
of the preceding list and the subjective element in the study of them
must be borne in mind.
If an area, as of the calf of the leg, be prepared, by cutting short
the small hairs, and examined, it is found that there are about 15
touch spots in each square centimetre, which is about one-fifth of a
square inch.
In another area so treated the hairs are counted and the following
result is given:--
1. On the dorsal surface of the forearm 78 touch spots are found in
an area containing 15 hairs.
2. On the flexor surface of the forearm 147 touch spots are found in
an area containing 22 hairs.
3. On the scalp 66 touch spots are found in an area containing 38
hairs.
Schäfer says: “An area of the dorsum of the distal phalanx of a
finger contains about seven times as many touch spots as an equal
area between the shoulders. Regions poor in touch spots are the
flexor surface of the upper arm, the upper third of the thigh, the
leg above the inner malleolus, the neck, and in general the skin over
subcutaneous surfaces of bone.”[81]
[81] Schäfer’s _Text-Book of Physiology_.
TABLE IV.--_Distribution of Cold and Warmth Sensations._
The Scale includes twelve grades of sensation in cold, and eight in
warmth sensations, and commences with the regions which yield the
maximal intensity of sensation.
_Cold Sensations._
1. Tips of fingers and toes, malleoli, ankle.
2. Other regions of digits, tip of nose, olecranon.
3. Chin, palm, gums, glabella (a small central area just above bridge
of nose).
4. Occiput, patella, wrist.
5. Clavicle, neck, forehead, tongue.
6. Buttock, upper eyelid.
7. Lower eyelid, popliteal space, sole, cheek.
8. Inner aspect of thigh, arm above elbow.
9. Intercostal spaces along region of axillary line.
10. Areola of mamma.
11. Nipple, flank.
12. Certain areas of loins and abdomen.
_Warmth Sensations._
Absent from lower gums, mucosa of cheek at second lower molar and
cornea.
1. Tips of fingers and toes, cavity of mouth, conjunctiva, patella.
2. Remaining surfaces of digits, middle of forehead, olecranon.
3. Glabella, chin, clavicle.
4. Palm, buttock, popliteal space.
5. Neck.
6. Back.
7. Lower eyelid, cheek.
8. Nipple, loin.
TABLE V.--_Distribution of Cold and Warmth Spots._
By stimulation of cold or warmth spots there is shown, not only
the quality and quantity of the stimulus, but the locality. When
punctiform stimuli are applied to pairs of cold spots and pairs of
warmth spots marked “local sign” is found. This Goldscheider showed
to be higher for cold than warmth spots.
Cold Spots. Warmth Spots
Palm .8 mm. Do. 2 mm.
Cheek, Chin and
forehead 0.8 mm. Do. 5.0 mm.
Upper arm 2 mm. Do. 3 mm.
Back of hand, leg,
thigh 3 mm. Do. 4 mm.
Forearm 3 mm. Do. 3 mm.
Back, chest, abdomen 2 mm. Do. 5 mm.
Thus on the palm of the hand two pairs of cold spots .8 mm. apart
are distinguished by this punctiform stimulation, whereas on this
surface two pairs of warmth spots are only distinguished when they
are 2 mm. apart on the cheek, chin or forehead and cold spots are
distinguished when .8 mm. apart on the same surfaces warmth spots
when 5 mm. apart.
TABLE VI.--Average lowest distances in millimetres on different areas
of skin where two points are felt as two or minimal distances from
which double sensation is obtained.
Skin Region. Adult Man. Boy aged Twelve.
Tip of tongue 1.1 1.1
Palmar surface of tip of
finger (index) 2.3 1.7
Red surface of lip 4.5 3.9
Palmar surface of 2nd
phalanx of finger 4.5 3.9
Dorsal surface of 3rd phalanx
of finger 6.8 4.5
Side of tongue 9.0 6.8
Tongue 27 mm. from tip 9.0 6.8
Plantar surface of distal
phalanx of great toe 11.3 6.8
Surface of palm of hand 11.3 9.0
Dorsal surface 2nd phalanx
of finger 11.3 9.0
Forehead 22.6 18.0
Back of ankle 22.6 20.3
Back of hand 31.6 22.6
Forearm and leg 40.6 36.1
Dorsal surface of foot 40.6 36.1
Surface on outer border of
sternum 45.1 38.8
Back of neck 54.1 36.1
Middle of back 67.1 31.6 to 40.6
Upper arm and thigh 67.1 31.6 to 40.6
TABLE VII.--(_According to Weber’s Law._) Average differences in
different regions of skin of sensation of pressure.
Forehead }
Lips }
Dorsum of tongue } 1/30 to 1/40
Cheeks }
Temple }
Finger nail }
Dorsal surface of forearm, leg, }
and thigh }
Dorsal surface of hand }
Dorsal surface of 1st and 2nd } 1/10 to 1/20
phalanges of fingers }
Palmar surface of finger }
Palmar surface of hand }
Flexor surface of forearm }
Dorsum of foot }
Dorsal surface of toes }
Plantar surface of toes } More than 1/10
Sole of foot }
Surface of leg and thigh }
Thus on the forehead differences of pressure are distinguished when
they are increased by 1/30, whereas on the dorsum of the foot they
have to be increased by 1/10 to be distinguished. This is carried out
by impact of little balls of a light substances such as pith.
It may be remarked of these tabulated results that on the one hand
they are the results of work extending over some seventy years and
numerous observers, and on the other that, broadly looked at, _they all
tell the same story_ of stimuli in their incidence on the skin--those
of pain, cold, warmth and touch. There is also one thread of origin
running through all, and that is that the regions most exposed to the
four stimuli show the highest development of specialised function and
structure.
Some Aspects of the Nervous System.
It has been said with some truth that the telephone has struck a
mortal blow at such serenity of life as the Juggernaut Car of modern
progress has left us. But if it has done nothing else it has furnished
the physiologist with a good illustration when he sets out to expound
the functions and arrangement of the elements of the central nervous
system and its peripheral expansion. In addition to this general
light upon a great matter the vivid experience of many an Englishman
during the recent years of war adds point to a subordinate phase of
the general story of the telephone, for it represents my contention
as to the origin or initiative of the sensorial areas of the mosaic
under consideration. Modern persons may be divided into two classes,
those who want and those who do not want the telephone, and the former
may be sub-divided into A, those who can, and B those who cannot
get it (or could not). A and B from the present point of view may
be termed Receptors, though to call the B people by that name is to
speak Hibernically. With this war-time experience in our minds, we
may picture a vast period of time during which the stimuli of pain,
cold, warmth and touch were hammering on the skin both before it
began to lose its chief hairy covering, and after that process had
left man still a hairy animal, but with much-diminished amount of his
ancient heritage. These stimuli fell upon the skin very much as the
class A, among telephone receptors, spent numerous fruitless stimuli
on Postmasters-General, Ministers in Parliament and in “short” bitter
letters to our bright little _Daily Pope_, and who yet found themselves
not “connected up,” as the saying goes. There is no knowing how long
it was before they had enough effect on the delicate nerve fibrils
struggling up into the epidermis and produced receptors or were
“connected up” to the exchange or central nervous system. I am inclined
to liken the pain stimuli to the short letters referred to, the cold
and warmth stimuli to those addressed to the Postmasters-General and
the touch stimuli to those which fell upon Ministers at question time.
Another comparison of the peripheral portion of the nervous system to
common things has at times forced itself upon my mind when reflecting
on the stimuli which are continually assaulting the skin, as I have
watched on the Needles’ Downs a flock of sheep on a summer evening
returning to their fold. As the sun begins to set they are scattered
over the western end of the Downs, still cropping the short grass
clothing those chalk and flint slopes which from immemorial time has
alone flourished there. They wander singly or in small groups on such
parts of the slope as the intrusive golfer still allows, and gradually
fall into larger groups which follow somewhat indefinite paths. As
they move further and further towards home they are seen to follow
one another in single file on some score or more of clearer paths,
and finally converge into one well-beaten and broad path until they
descend the northern slope and pass out by a single roadway into which
a gate opens, and so reach the haven where they would be. Here one has
a simple picture of the common stimuli of the skin, at first indefinite
and ineffectual, by their cumulative action producing an individual
receptor and its nerve connection with the central system.
Professor Leonard Hill[82] also gives a view of the general action of
the nervous system and compares it to control of the police force. He
supposes a murder to have been committed in a village, and that the
local policeman telegraphs to the local town ordering the roads to
be searched. The policeman is the tactile sense-organ, the telegraph
wire is the sensory nerve, the telegraph office in the local town
is the spinal cord, from this office a message is sent to the town
police-station by another wire and the police are set in motion. The
police are the muscles, the wire that sets them in motion in the motor
nerve. The message is also sent to neighbouring towns and to London,
that is to say, other local offices (parts of the spinal cord) and the
head office (the brain) are informed of the crime or sensory impulse.
The central office in London directs the operations controlling the
local police office. The whole order of events need not be here
described because it goes beyond my immediate purpose, but it is enough
to say that attached to the head office are the cleverest detectives
(higher sense-organs) and in these are kept records of past crimes,
lines of action of the police, and success or non-success of their
investigations.
[82] _Manual of Human Physiology._ Leonard Hill, p. 369.
Following on this picture he speaks of the way in which conscious
actions become automatic and makes a statement to the effect that
“_There is evidence to show that the axons_ (or processes of the
nerve-cells which extend unbroken from nerve-cell to its termination)
_become covered with a adulated coat as each new tract is formed. Thus
the structure, like the habit, becomes fixed_”--and--“_It would appear
as if, by repeated experiences, tracts and pathways must be beaten
through the nervous system_”[83] (Italics not in original).
[83] _Op. cit._, p. 371.
Beside this I place a statement from Professor Graham Kerr as to his
view of the development of peripheral nerve-trunks. He is reviewing
the “outgrowth” theory of His, the “chain cell” theory of Balfour, and
the “Primitive Continuity” theory of Hensen, and expresses himself as
follows: “_It is suggested that the development of the actual nerve
fibril is simply the coming into view of a pathway produced by the
repeated passage of nerve impulses over a given route._”[84] (Italics
not in original.)
[84] _Text Book of Embryology._ Vertebrata with the exception of
Mammalia. Vol. II., 1919, p. 106.
A passage from Professor McDougall’s _Physiological Psychology_ may
also be referred to at more length than it was in Chapter III.,
page 25. Speaking of the automatization of voluntarily acquired actions
which have been explained by the view that purely reflex actions
carried out by mechanisms of the spinal level were also originally
acquired by our original ancestors as voluntary actions, he says, “This
view is usually associated with the name of Wundt, who has forcibly
advocated it. It implies, of course, the assumption that acquired
characters are in some degree transmitted from one generation to
another, a proposition which most biologists at the present time are
inclined to deny because they cannot conceive how such transmissions
can be effected. Nevertheless, the rejection of this view leaves
us with insuperable difficulties when we attempt to account for
the evolution of the nervous system, and there are no established
facts with which it is incompatible. If, therefore, we accept this
view we shall regard the congenital neural dispositions, both those
that determine pure reflexes and those that determine instinctive
actions, as having been acquired and consolidated under the guidance
of individual experience, with the co-operation, to a degree which we
cannot determine, of natural selection.”[85]
[85] _Physiological Psychology._ W. McDougall, p. 156 (1911).
These three statements from a physiologist, a zoologist, and a
psychologist, all of great eminence, though they differ in particular
problems studied, tell very strongly in favour of the position here put
forward as to initiative in the production of specialised innervation
of the skin.
Origin of Cold, Warm, Pain and Touch Spots.
The hair-clad skin of primitive man provided ample raw material for
the eventual differentiation of both end-organs and sensorial areas
which is found to-day. Not only did he possess what is called Common
Sensation in his skin but in the individual hairs lay a delicate
tactile structure, which, though probably inferior in delicacy, serves
a similar purpose to that of the vibrissæ on the muzzle of Felidæ. Each
hair, being deeply inserted into the skin and supplied with fine nerve
fibrils, when it is bent, acts as a lever communicating an impulse
to an afferent nerve trunk In an animal covered with thick hair the
sensory impulse conveyed might be exceedingly delicate, but, from the
nature of the case, of much more limited range than in one like man in
whom the hair is so greatly diminished in length and thickness.
It would be fruitless to speculate as to which of these four forms of
stimuli was the earliest to become effective in developing man.
Cold and Pain.
Two of them, cold and pain, may be termed _nocuous_; one, that of
touch, _useful_, and one, that of warmth, _indifferent_. If it be true,
as Professor Scott Elliott states,[86] that man’s earliest home had a
climate which “lies between the regular tropical, with wet, steaming,
impassable jungles, and the colder temperate zone, so affording chance
of acclimatisation in both directions,” the stimuli of cold would even
then not be wanting, however much they increased in severity when he
passed through glacial periods; but wherever, whenever, and at whatever
time he first became man he had to tread the Via Dolorosa in the course
of his hard and eventful life, and must have been well accustomed in
all regions of his skin to the stimuli of pain, working, as he did, for
his living, and fighting for it and his mate, with varied and powerful
enemies. Though it is correct to call both these fundamental stimuli
“nocuous,” this is all a matter of degree, and both the stimulus of
moderate cold, raising blood-pressure and activating metabolism, and
that of minor pains, would do little else than good in his education
for the higher terrestrial life to which he had descended. If he was
to learn effectually to take care of himself the discipline of both
moderate cold and pain would be as valuable to him then as in its
measure it is to his descendant to-day. The triumphs of medicine and
surgery could never have appeared if it were not for the beneficent
warning voice of pain that so generally accompanies disease.
[86] _Prehistoric Man and His Story_, p. 92.
Through long ages of exposure to the stimuli of cold and pain came
response in the form of cold and pain spots, after minute struggles
between the static conservative tissues of the skin and the dynamic
force of repeated assaults upon them. In due time then receptors
appeared and each became connected with the central organs, by which
means better adapted motor reactions against “nocuous” cold and pain
became possible. In 1900 Professor Sherrington summed up the evidence
in Schafer’s work on Physiology against the existence “of separate
afferent fibres with their specific end-organs entrusted specifically
with carrying painful impressions to a pain centre,” but Professor
Starling in his later work on Human Physiology speaks of “a distinct
sense of pain,” probably subserved by a distinct set of nerve fibres,
but for the present purpose it is not necessary that agreement on such
a problem should be reached, for it is alone with pain _spots_ that we
are concerned. He also points out that on the one hand the cornea is
sensitive to only one of the four stimuli in question, that is, pain,
and on the other that the surface of the glans penis is sensitive to
cold and pain, but tactile sensation and warmth sensations are almost
entirely absent.
_Touch._--This form of stimulus and its response can only be reckoned
as useful to the organism, except that it may be, and often must be
indifferent. The great number of the touch spots can be understood
when it is declared by Professor Sherrington that almost invariably
there are one or more touch spots close to the emergence of each
hair,[87] and that they are very numerous also on the palmar and
plantar surfaces of the hand and foot. Of the four forms of cutaneous
stimuli those of touch are the only kind that have so far been proved
to have specialised corpuscles, the other three having developed the
physiological equivalent of cold, pain and warmth _spots_.
[87] _Schafer_, p. 922.
_Warmth spots_ are decidedly the least numerous of the four, those of
pain being, as stated by Professor Sherrington, the most numerous. It
is obvious that unless thermal stimuli become somewhat excessive they
hardly can be described as “stimuli,” being more or less neutral in
their action on a warm-blooded animal. This cannot be entirely so,
because it has been shown quite conclusively that warmth spots _do_
exist, though much less numerous than others. There is a significant
fact as to thermal reaction and that is that there are no pure
_heat_ spots like those of cold, for the stimuli of about 49° C
are so associated with those of pain that warmth spots alone are
distinguished, and among primitive man no stimuli of heat could impinge
on his skin, until he had learned the use of fire, more powerful than
those of solar heat.
Such stimuli of heat as the rays of the sun would occasionally
discharge on the skin would resolve themselves into the general
stimulus of pain, and in this direction a far shorter initiation
occurred than with any of the four normal cutaneous stimuli. The fact,
at any rate, of there being no _heat_ spots is to be noted.
It remains now, having quoted three writers eminent in physiology,
psychology and zoology in support of the modest thesis here put
forward for me to appeal to the authority of the facts contained in the
tables for such evidence as they can give, and to give a summary of
this.
Summary.
1. Table I. shows that the structures known as touch corpuscles are
distributed on those parts of the skin where the stimuli of touch fall
most and in proportion to the degree in which those parts are employed
in tactile discrimination; thus, most of all on the index finger (with
the exception of the tip of the tongue) next on the thumb and less on
the middle finger. There are 530 of these corpuscles to the upper and
317 to the lower extremity.
2. Table II. bears out the same conclusion, the average number of
corpuscles to a square millimetre being twenty-one on the terminal,
eight on the second and four on the first phalanges of the index
finger, whereas on the foot there are seven on the great toe much
exposed to stimuli and only two on the middle of the sole of the
foot, which is little exposed. The absence of them from the cornea
and conjunctiva, protected by quick and powerful reflexes from such
stimuli, and from the (normally) covered glans penis is in accordance
with the other results.
3. Table III. dealing with touch spots, shows that these are nearly
twice as numerous on the flexor as the dorsal surface of the forearm;
and nearly five times as numerous as on the scalp, where tactile
stimuli are few, and that the distal phalanx of a finger contains about
seven times as many as an area between the shoulders. The regions poor
in touch spots are shown to be those where relatively few tactile
stimuli can fall.
4. Table IV. gives cold and warmth sensations graded according to the
delicacy with which they are perceived in many regions of the skin.
The cold sensations are best distinguished on the parts normally most
exposed to cold, as the tips of fingers, malleoli, tip of nose, chin,
patella, wrist, and least on the protected areas, inner side of thigh,
flank, loins and abdomen. The warmth sensations are best distinguished
on the regions on which the stimuli of warmth has most frequently
fallen, tips of fingers and toes, cavity of mouth, palm of hand, less
so on the neck and loin. And the striking fact is noted that warmth
sensations are not felt in the lower gums, the inside of the cheek at
a certain level and the cornea, which again is protected from these
stimuli by its efficient reflex, whereas to the gums and inside of the
cheek most warmth stimuli have not been “stimuli” at all.
5. Table V. also gives results of the mode of distribution of cold
and warmth spots, examined with punctiform stimuli. The “local sign”
for cold is higher than that for warmth spots, and two of these
are distinguished as double when only 0.8 millimetres apart on the
palm, cheek, chin and forehead, whereas on the upper arm, back and
thigh, they are only distinguished as double when separated by two
millimetres, and this distance is the minimum at which warmth spots are
distinguished as two, that is 2 mm. on the palm, and five on cheek,
chin, forehead and back. This tells the same story as Table IV., of
past stimuli of cold and warmth.
6. Table VI. deals more elaborately than the others with double
sensation in different areas of the skin, the tip of the tongue being
the most accurate in this respect of all examined, and the tip of the
index finger next, which is to the great toe as 2.3 to 11.3, the palmar
surface of a finger half as accurate again as the dorsal surface, the
palm of the hand twice as accurate as the surfaces of the forehead and
back of ankle, nearly four times as much so as the dorsum of the foot
and six times as the skin of the middle of the back.
There is here a very close relation between the amount of exposure of
these various regions to tactile stimuli and their present equipment of
ability to discriminate between two small objects.
7. Table VII. deals with the sensation of pressure in certain groups of
areas, and shows that change of pressure is perceived about three or
four times as accurately on the forehead, lips and tongue, as on the
finger nail, back of forearm, hand, or fingers, and more than three or
four times on the back of the foot, and sole, and surface of leg and
thigh. In this group of observations also the rule is followed that
the greater and more frequent in man’s ancestral past have been the
exposure of his skin to variations of pressure, the greater is his
present power of accurate discrimination of them.
There are some scattered facts mentioned by Professor Sherrington
which are in keeping with the line here taken, that the formation of
receptors in the skin have their origin in accumulated stimuli. He
refers to the vain endeavours of Goltz to evoke the reflex croak of
the female frog by applying electrical stimuli to the skin, whereas
non-nocuous mechanical stimuli were the only stimuli that proved
effective.
He never was able to elicit the “extensor thrust” in the “spinal dog”
by any form of _electrical_ stimulation, but only by a particular kind
of mechanical stimulus. This peculiarity was also found in the pinna
reflex of the cat.
As to the scratch reflex in the dog it was only when it was _easily
elicitable_ that it could be evoked by electrical stimulation as well
as mechanical, and when it was not easily elicitable electrical stimuli
failed altogether while mechanical stimuli still evoked it.
He describes the receptor as a mechanism “_attuned_ to respond
specially to a certain one or ones of the agencies that act as stimuli
to the body,” and points to the fact that _electrical_ stimuli are
not of common occurrence in nature and no chance for adaptation to
evolve in the organism receptors appropriate for such stimuli has
been afforded. Such negative facts are at the least suggestive in
considering the question of the mode of origin of receptors and
end-organs, electrical stimuli being rare in nature.
The subject of the innervation of the skin and its receptors has been
treated here in a great measure by the aid of imagination, with some
evidence, and a good deal of reconstruction has been attempted, but
perhaps this will be pardoned by those who are prepared to carry out
a corresponding process with such as Pithecanthropus, Eoanthropus and
Saurian monsters from somewhat scanty osseous remains. Any biological
theory of the origin of these receptors than the one here put forward
is faced with some formidable difficulties, which are probably
insurmountable.
CHAPTER XXIV.
THE BUILDING OF REFLEX ARCS.
Assuming the foregoing origin of the innervation of the skin, I submit
that between this rudimentary process and the building of sensori-motor
arcs in the spinal cord and brain there is a field, almost unlimited,
for initiative in the construction of new forms of animal life. The
former is nothing without the latter. To leave it without proceeding
further is to leave it “in the air” as military writers say. The
formation of Receptors, then, both in the skin field and in the higher
sense-organs, leads of necessity to the formation, multiplication and
co-ordination of reflex arcs. As in an imperfectly organised telephone
service after many a repeated stimuli or “rings” the messages begin to
reach their destinations, and as by practice the operators better and
better learn their business, so the impulses passing through receptors
and nerve-fibrils become organized into more or less efficient systems
of arcs, and response is secured to them by some effector of gland or
muscle. It is not true of man alone that practice makes perfect.
A certain feature of higher animals which distinguishes them from lower
must be remembered, and that is that among them the individual becomes
increasingly important. Speaking generally, the latter are born and die
in large groups, and their lives resemble those of their group more
closely than in the former. The struggle of the individual is vividly
pictured by Professor Woods Jones in his description of the baby of the
perfected arboreal animals. He shows how they and the roaming Ungulates
and Pelagic Cetacea cannot indulge in large families, and that it is
only those forms which have a safe retreat for their young which can
avoid reduction of the size of their families, and how the higher apes
still more resemble in these respects mankind, as we know it. For
the proper study of the “synthesis of the individual” organism this
essential fact must be kept in mind.
Some Illustrations.
It will be expected of course that for the claim here advanced on
behalf of the predominant influence of the nervous system in the
initiative of the evolutionary process some experimental or other
evidence should be produced. Before entering upon this, I think some
analogous facts from the story of man, in accordance with the principle
laid down in the first chapter should be stated, so as to illustrate
the line of thought. These will be in the nature of analogies, and
whether or not the accepted accounts of the chosen examples agree
precisely with the last word of the critics is immaterial, for if not
they will equally well serve the purpose of illustration.
Abraham.
When from his Mesopotamian home an opulent and successful farmer
decided for reasons sufficient to himself that he would leave his
present prosperity for a promised land, and went out not knowing
whither he went, it is manifest that the construction and organization
of Abraham’s cerebral cortex was the motive power which led to this
step so fraught with change to himself, his descendants, and the
world. By his choice he showed the inherited structure of his brain,
its nature, and perhaps its nurture, to be different from those of his
family and tribe. Implicit in this venture was the introduction of a
new group of people into a new environment, and their reaction to it
through many generations is written before our eyes to-day in indelible
characters. It was neither stature, muscular development, colour of
hair, skin or eyes, properties of digestive or circulatory organs,
keenness of sight, hearing, taste, smell, or touch which led to this
result even though without a high degree of efficiency of these he
could never have “arrived” as he did.
Mohammed.
The conjunction of environment with a certain organized complexity of
grey matter was hardly ever more important to the world than that of
Mohammed. The powerful frame, abundant black hair, wonderful dark eyes,
and great imposing head may well have attracted the rich widow who
“made his fortune” by marrying him, and they stood him in good stead in
his later adventurous career. But nothing short of a unique arrangement
of his reflex-arcs, chiefly in the association-areas of his brain,
could have opened up to him the world of Asia and Europe.
Columbus.
Who can doubt that it was ultimately to the inherited structure of the
convolutions of his brain that Columbus owed his great achievement
in opening up a New World; or that to the reactionary and intense
“character” of Philip’s brain the persecutions in the Netherlands were
due; and on the other hand that to the brain of William of Orange
with its liberal and enlightened “character” the Seven Provinces that
resisted Philip owed their freedom; the results in the two cases being
the decay of Spain from that time forward, and the final success in
the struggle for religious liberty. In such a view of historical facts
it is not necessary either to follow Carlyle in his extreme claims for
the influence of great men and heroes, nor to look upon the hero as an
epiphenomenon. It is certain that eventually some other great man would
have arisen to do what the great Genoese did, if he had not done it,
and as it is claimed that Amerigo di Vespucci did, and it is certain
that Philip was only the last of the Hapsburg sovereigns who determined
the fall of Spain, and that Huss, Jerome, Wycliffe and Luther in their
days initiated the struggle for religious liberty which Holland brought
to success. But the facts referred to can hardly be disputed, and the
men and their “characters” did certainly determine permanent changes in
the world.
Napoleon.
Among individual men of modern times none strikes the imagination
as does Napoleon. Without ignoring the tremendous outburst of the
soul of down-trodden France at the Revolution, it cannot be denied
that the “character” or grey matter of brain of the man of whom it
is said “nothing where he had passed was as it had been before,” was
the dominant and natural fact that changed the face of Europe. What
physical quality had Napoleon, except those of his grey cells, which
could have led him to such results on the environment into which he was
cast?
Migrations.
Similar results in nations and tribes can easily be supplied from
the great migrations of the past. The wider movements are but due to
comparatively small aggregates of adventurous men, in other words to
the aggregation of many similar central nervous systems. The great
Western and Southern adventures of the Scythian Tribes had many
contributing causes on which the historian has much to say, and they
were physically highly efficient for their new career, but, reduced
to the simplest elements, it was neither their great stature, strong
muscles, flaxen hair, nor blue eyes, but the cerebral constitution of
a comparatively small group of them which brought part of the nation
to the promised land, and left another and large part in their homes
beyond and along the Danube. The subsequent story of the latter may
well be compared with the invaders of Gaul and Italy in connection with
initiative in evolution.
The successive invasion of Britain by Low German tribes in the fifth
century, and the Scandinavian hordes of Swedes, Danes, Norwegians,
Letts and Finns in the eighth and ninth teach the same lesson. The
later condition and development of the Northmen in France, Italy,
Spain, Sicily and Britain have only to be compared for a moment with
that of their races who remained in Norway, Sweden and Denmark and
their descendants, to bring clearly before one’s mind the profound
influence exerted by the cerebral constitution of the original Viking
hosts on their career in their new environments, and, indeed, on the
environments themselves; as in intermarriage with their conquered foes.
These examples have been chosen for the reason that one feature is
common to them all, the introduction of an individual or group into
new environments by reason of the constitution of their brains,
irrespective of the contributing factors. If these be sound analogies
they bear closely on the matter of initiative in the evolution of new
forms of life. The men in question came to their task, in their day,
with a certain equipment of brain derived from many ancestors and much
nurture. Unconscious arbiters of their fate and that of multitudes who
should follow them, they initiated a course of physical and cerebral
evolution of which we can see much revealed before our eyes. The motive
power of their conduct bears a relation to their physical forms that
the engines of a motor-car do to its varied forms of body. The latter
are modified indefinitely to suit convenience, comfort and grace, but
fundamentally they exist and are energised by the former, just as
structure is modified for the performance of function.
This fact is occasionally brought vividly to the mind of an observer
when he first passes a Rolls-Royce car in all its glory and
magnificence, and then a rough squalid kind of trolly in which the
engine-parts of a similar future Rolls-Royce are out for trial. In
principle it is not a long step from these illustrations to the diverse
environments of animals in which their lot is cast, and their reaction
to them as to behaviour and structural change.
Some Changes in Habits of Man.
There are two current views as to the present erect posture of man,
one which traces it to the adoption of a new posture by a pronograde
four-footed ancestor, and the other that man’s ancestors were “never
typically pronograde with four supporting limbs,” but derived from an
arboreal stock in which the forelimbs were mobile rather than stable.
Whenever or wherever man became orthograde he opened up for himself
and his descendants immense regions of structural and functional
change and became increasingly dominant over his environment. Changes
in muscles, joints, bones, bursæ, lungs, heart, and vessels occurred
through his employing in new modes the muscles, joints, bones, bursæ,
lungs, heart and vessels he already possessed, and the resemblance
between these structures of man and the great apes has given to the
latter the name of anthropoid, and this similarity of structures
in the highest Primates has done much to support in the past that
Simian origin of man which is at present questioned. The behaviour
of the apes and early man were sufficiently alike to lead either to
a parallel or genetic similarity. This point is, perhaps, irrelevant
in considering the great field for initiative in the formation of
new physical characters, and chief among these new reflex-arcs which
have built up the marvellous organ of man’s glory and greatness; but
no one can dispute the elementary fact that the ancestor of man who
adopted terrestrial bipedal locomotion and became orthograde, owed it
to his growing brain and the higher integration of his organs for that
function. But besides the new posture he had adopted he learned to talk
articulately, to make tools, and to use stereoscopic vision. None of
these could have been started on the upward way without a long process
of trial and error in the course of his total experience and practice
of his powers. The results that followed from these three properties of
his are inconceivably great, and it is unnecessary to enlarge on such a
theme or to add to the number of examples.
Leaving, then, the immediate ancestor to work out his own destiny in
his new terrestrial home, we must as before proceed backward in the
history of animal life in the line of Primate ancestry.
Primate Ancestry.
It is generally agreed to trace the Primates back to an active pioneer
animal form which took to the trees, and which arose out of the
widely-spread Insectivores. This derivation will probably satisfy
any reasonable genealogist. But, if we may use a parallel in human
families, this active animal was as different from its congeners as
Napoleon was from his four brothers who played a part in European
history, and it is not necessary to say more as to the significance of
this fact than that the relative importance of “chassis” and “body” is
again a useful analogy. But we need to ask what those congeners did
if we are to succeed in understanding the Napoleon-like course of him
who became our Primate ancestor. From the original widely-spread and
plastic raw material of the Insectivores allied forms took different
lines, and their stories are written at great length in one small
and the three other great orders of Bats, Carnivores, Ungulates, and
Rodents. As it has been pointed out, Carnivores took to attacking
larger prey, including their less fortunate relatives, and stepped
into the arena as carnivorous animals; the Ungulates-to-be became
herbivorous and developed into two great groups of hoofed animals,
relying mainly on flight for safety; Rodents took to burrows for
defence, ceased to trouble much about attack, and became gnawing
animals; Bats adopted an aerial life--a poor form of it indeed like
that of the aeroplane--and acquired a degraded fore-limb. Before
leaving these great orders of animals, whom I do not desire to compare
unfavourably with poor Louis, Jerome, Joseph or Lucien Bonaparte, it is
convenient here to refer to a fact which comes to light immediately one
looks into such a piece of classification as this of the orders arising
out of the loins of the early Insectivores, and that is the functional
conception underlying it. Doubtless pure functional “characters”
could never supply a whole system of classification in the light of
the modern doctrine of descent with modification, and of zoological
affinities. This is shown in a change from division of six orders of
Birds-Running, Swimming, Wading, Climbing, Predatory and Perching
Birds, to that of a few old-fashioned Ratite Birds, and all the rest,
one which seems the best that can be offered at present.
Insects, Mollusca, Birds.
The grouping of animals by structural characters, and by affinities
which are assumed, though based on almost undeniable evidence, whether
into species, families, classes, phyla or sub-phyla, has its apotheosis
in Mollusca and Insects. As to the second of these immense groups
it has always seemed strange that their colourings and structural
characters should have received such intensive study from Weismann to
the exclusion of Mollusca, when he set out to prove his stupendous
negative, and still more that of Vertebrates, among which his chief
difficulty and desired triumph would seem to have lain. Mollusca though
invertebrate are held by many to be in the line of ancestry of the
highest forms of life, and at any rate insects are not. They are most
fruitful fields indeed in which Nature has been able to show what she
could do by her stern selective powers, but, from the point of view of
descent with modification, may be fairly compared to a review of an
army in time of peace, or the Kriegspiel of a German military staff. He
who concerns himself with the fundamental difficulties of the problems
at issue in evolution must make his notes of what experts tell him of
such groups as those of Insects, Mollusca and Birds, and pass on to the
higher forms in which on the one hand function becomes the predominant
partner, and on the other individual experience becomes more and more
important. He feels indeed at liberty to wish the entomologist and
ornithologist all success, and to leave him at peace, in his siding, to
pursue his delightful and interminable studies far from the dust and
din of controversy.
Insectivores.
The critical territory of vertebrate, and still more of Mammalian
forms, in which the genealogist pictures the five main groups of
Insectivores, looking about them, if one may so speak, in the world
around and pondering which of many paths they shall pursue, resembles
certain centres that may be seen in towns where three, four, five,
or seven different roads are open to the traveller, each with its
incalculable effects on his ultimate career. If one may change here the
metaphor it may be said that the Insectivores are the watershed of the
Five Rivers of higher life. However much the wayfaring insect-feeders
have diverged from this broad centre in structure, and however much
the laws of genetics have widened this divergence, the facts of
function stare one in the face when such descriptions of three of the
four orders outside the Primate stock are pondered--Flesh-feeders,
Herbivorous animals, Burrowers and Gnawers. These time-honoured names
appealed strongly to older zoologists, and in them is implicit a large
body of evidence for initiative in their evolution by pioneering work
on the part of their ancestors. Though in these days Prototheria
include Monotremes, One-vent animals, Metatheria, Marsupials or pouched
animals, and Eutheria Insect-feeders, and though Mammals derive
their indispensable name from the function by which they feed their
young, the most severe of systematists cannot clear his mind from
the old leaven of function in all these terms. They imply momentous
potentialities prior to new structures, and the modern fails to ban
entirely such functional names. I believe there is here no juggling
with names and words on my part, but a stone in the foundation of the
unambitious building which I am seeking to rear. It is ultimately
connected with a directive power as well as the formation of
sensori-motor arcs in the central nervous system.
Is it possible or probable that the factors which led some group to the
water alone, some to a life in water and on land at different parts
of their lives, some to a crawling life on land and partly in water,
some to the air and trees, some to nocturnal, some to hybernating, some
to burrowing life, some to a diet of flesh, some to one of plants,
some to the trees alone, some to the trees and land, some to the
land by night and trees by day, and some for ever and wholly to the
land--is it probable that any process of selection of suited structures
with countless ages of trial and error, could have determined these
changes of habit and habitat? At least one may claim that the balance
of probabilities is heavily against that view, and that the forging
of reflex-arcs, with all it means to the career of an individual,
affords a more intelligible hypothesis, and that this is strongly
supported by modern discoveries and doctrines arising from the work of
physiologists, as will appear later.
The Place of the Nervous System in Evolution.
The constitution of the nervous system is conditioned by conduction,
its fundamental and primary function. Its processes consist in the
transmission of impulses from receptive fields to effective reactions
through devious paths in a region which, even to-day, is a jungle, with
many further secrets for physiology to reveal. From this point of view
the nervous system may be looked at as a clearing-house and storehouse
of impulses _on their way in_, _on their way through_, and _on their
way out_. If so, the making of new reflex-arcs is a process which has
gone on simultaneously with the formation of receptors in the skin,
the higher sense-organs and such deep structures as muscles, and that
of effectors of infinite variety--and these are called conveniently
adaptations. When we hear from Professor Sherrington that the afferent
fibres with their private paths which enter the spinal cord outnumber
three times those which leave it, and that those of the cranial nerves
should be added, so that the afferent fibres may be reckoned as five
times more numerous than the efferent, we get a vivid idea of the
fundamental importance of the formation and compounding of reflex-arcs
into systems. Without that the most sensitive receptors and the widest
range of structures and organs, small and great, would be as nothing
and things of naught.
A neurone is the anatomical, as the reflex-arc is the functional unit
of a central nervous system. Just as it is profitless to consider apart
the engines and body of a motor car, as working machine, so is it to
picture neurones and reflex-arcs separately in the living nervous
system except for the purpose of an ideal construction. In common with
the organs and structures of higher animals they have to pass, as
historical structures, through the stages of initiation, repetition
of rudimentary function, and selection by trial and error, till the
“canalizing force of habit” issues in rudimentary and increasingly
efficient effectors. It is in this final stage where the triumphs of
selection have been won, and where their undeniable value and interest
has led some exponents of the distributional laws of genetics to
disregard, or accept as data, the early and formative stages. Theirs
is a mental state which resembles that of Darwin, who, for once in a
moment of haste, declared the question of the origin of life to be
rubbish.
In the foregoing consideration of the formation of receptors of the
skin it was assumed that certain common stimuli of the environment
hammer out for themselves paths in the nerve-fibrils of the skin and
by ceaseless repetition lay down not only the receptor, which may
be called the _terminus a quo_, but also the afferent fibres which
ultimately find their way into the grey matter of the cord and brain.
That this is the initial stage of the construction of the higher
nervous system can hardly be denied. But it carries the problem of the
synthesis of the organism but a little way unless it be coincident
with the construction of new reflex-arcs and their co-ordination
into systems. Till this stage be reached in a rudimentary form the
most cunning and exact adaptations and structures, or, as they may
be broadly called effectors, will not advance the efficiency of the
organism in the smallest degree. If the receptor be the _terminus
a quo_ the effector is the _terminus ad quem_. This is so obvious
that it may be waved aside as a truism not worth the notice of a
zoologist concerned with the major problems of biology. It may seem to
challenge in a highly speculative region and manner the labours of the
biometrician and Mendelian, but, if fairly met it no more encroaches
on their territory than do the labours of the engineers who invented
the first and crudest chassis of a motor car upon the elaborate and
brilliant ingenuity, taste and skill of the coachbuilders who turn
out the “body” of a sumptuous Rolls-Royce of 1920. But the latter
would never have “arrived” if the former had not made his slow and
arduous trials and errors and final success. So here, as in many other
subjects, a truism has its use. If the biometrician and Mendelian will
only abstain from erecting notice-boards to proclaim “No thoroughfare
here,” we shall not be put down as trespassers or poachers on their
ground and may range at large in certain fields of speculation.
Some Neural Phenomena.
Among numerous phenomena of nervous reactions discovered by the
research of physiologists certain have a close bearing on the formation
of receptors, afferent fibres and reflex-arcs, especially those
of Delay, Summation, Fatigue, Block or Resistance, Localization,
Facilitation and Inhibition.
Facilitation.
But of all these important reactions in nervous tissues none bears
so closely on the problem of the formation of reflex-arcs as that of
Facilitation. This is equivalent to the Law of Neural Habit of the
physiological psychologist, and is bound up with the highly important
Law of Forward Direction, which Professor Starling says might as well
be spoken of as the Irreciprocal conduction of nerve-arcs. The Law of
Forward Direction of sensori-motor arcs is too well known to need here
any description. But when this law is taken into account the phenomenon
of Facilitation is seen to throw a strong light upon the earliest
and rudimentary formation of specialized nerve-fibres, reflex-arcs
and Final Common Paths leading to the effector glands or muscles.
Facilitation is described shortly by Professor Starling as follows.
If the passage of a nervous impulse across a synapse or series of
synapses in the central nervous system be too often repeated, fatigue
is produced, and there is an increase of the block at each synapse.
If, however the stimulus be not excessive and the impulse not too
frequently evoked, the effect of a passage of an impulse once is to
diminish the resistance, so that a second application of the stimulus
provokes the reaction more easily, and he adds that the result of
summation of stimuli is in fact in the direction of removal of block.
When an impulse has passed once through a certain set of neurones to
the exclusion of others it will tend, other things being equal, to
take the same course on a future occasion, and each time it traverses
this path the resistance in the path will be smaller. Education then
is the laying down of nerve-channels in the central nervous system,
while still plastic, by this process of Facilitation along fit paths,
combined with inhibition (by pain) in the other unfit paths. He makes
the important statement that Facilitation is of great interest in
connection with the development of “long paths” in the central nervous
system and, _more especially with the acquirement of new reactions by
the higher animals_. (Italics not in the original).
Raw Materials of the Central Nervous System.
The raw materials of higher central nervous systems are furnished
even in lowly Vertebrates by the neurones and their processes, and
the pathways into the grey matter by the “canalizing force of habit”
in the receptors and afferent fibres. Facilitation, discovered in
higher Vertebrates, such as dogs and cats, throws backwards a light on
the earliest struggles towards success and integration among phyla,
sub-phyla and smaller groups, and here again the well-known may lead
to the less-known. We may then frame a legitimate hypothesis, or at
least an ideal construction of trials and errors and success, if those
of lower levels were ever to be introduced to the career of progress
and achievement. But to make good this claim it is necessary that it
be based on the important doctrine taught by Hughlings Jackson of the
three (or more) levels of sensori-motor arcs--those of the spinal or
lowest, of the sensory or intermediate, and those of the third or
highest level, in which the association-areas of the Primate brain are
at once the means and the title to his primacy, or headship of the
sentient world. The light of this doctrine guides the mind backwards to
the frog-stage of animal evolution with its highly organized congenital
system of arcs of the spinal level, so efficient for its life that,
even when the brain is removed, the frog can execute under certain
stimuli a purposeful complicated movement such as that of trying to
wipe away with its foot an irritant drop of acid applied to its head
or back; or, still more, if touched lightly between the scapulæ, will
“lower its head at the first touch, and again more so at a second,
and at a third will, besides lowering the head, draw the front half
of its trunk slightly backwards; at a fourth the same movement with
stronger retraction; at a fifth give an ineffectual sweep with its
hind or fore-foot; at a sixth a stronger sweep; at a seventh a feeble
jump; at an eighth a free jump, and so on.” Probably such an animal as
the frog has all its reflexes congenitally organized, whereas a dog,
reaching the sensory level, has added countless reflex-arcs to those
inherited from its early ancestors of the Insectivores which had long
emerged from the spinal level, retaining its old, perfecting its new
inheritance, and eliminating the unfit. Perhaps a faint picture of this
long process may be afforded by watching an experienced mountain guide
ascending an ice-slope with the aid of ice-axe, hand and foot.
Integration of Raw Materials.
Every group of animals in the higher ranks has its own entailed
property of innate reflexes, for example, the reflexes which subserve
the reflex functions of the cord: those of locomotion, muscular and
vascular tone, micturition, defæcation, impregnation and parturition.
These exist in an animal of the spinal level whether or not it
remains purely aquatic, partly aquatic, partly terrestrial, arboreal
or terrestrial. As the progressive groups ascend the ladder of life
they add to this inalienable heritage, gained we need not here ask
how, fresh reflex-arcs by response to new initial stimuli, forging
them by the incident of use. So, the original acquirements in the
past levels serve as starting points for raising the degree of their
nervous integration with growing control over their environments. The
long story from the simple central nervous system of a fish, with
a few or no association-areas, to that of man with his extensive
frontal, parietal, parieto-occipital association-areas, could never be
deciphered, even with the light of the laws of genetics turned on full,
without a protracted process of construction of fresh arcs. A common
illustration of such a series of changes and results may be seen in the
building of a house. Bricks, foundation-stones, walls and a roof may
serve some of the elementary requirements of a house and much less than
these were of use to early man for his shelter. Without them we cannot
call any structure a modern house; but also without floors, staircases,
windows, chimneys, division into rooms, some degree of decoration by
paint or paper, and a supply of water, we should refuse in these days
the name of house to that rough structure, apart from beauty of design,
decoration, within and without, and some addition of modern appliances
of comfort and convenience. In the history of house-building the stages
of supply of raw materials, adaptation to needs guided by selection,
initiation, trial and error have their counterpart in the construction
of higher animals.
Evidence.
It will be asked what evidence there is for the view here put forward
that such is the order and method of the construction of the central
nervous system. There are two classes of evidence. The first direct,
and the second indirect and resting on inference. The well-known leads
to the less-known and inferred. Direct evidence of the foundation
of new reflex-arcs and their organization is of course small. The
conditions, such as the duration of human life, preclude any extensive
formation under experiment of new reflex-arcs, but enough is known to
enable one to follow the backward way with some confidence. As to the
inheritance of these, the evidence rests on opinion and tremendous
probability, but as the only problem with which I am concerned here
is that of initiative I think it better to leave the matter of
transmission to a dispassionate consideration of the probability of its
occurrence.
Direct Evidence.
The prolonged researches of over twelve years of Professor Pawlow and
his colleagues on dogs afford a body of evidence as to the possibility
of producing new reflexes in the life of an individual which have
never been questioned. In 1913 at Groningen, before the International
Congress of Physiologists, he gave a brief account of this work. His
previous work on the digestive glands carried on by delicate operations
in which the œsophagus was diverted from the stomach and made to open
externally, and in which a portion of the stomach was diverted from the
rest and a new “small stomach” was formed, gave him the opportunity
of immensely important insight into the factors governing the work of
the various glands of the stomach. The work of others showed similar
results in the pancreas. I only refer to these because they lead up to
the special artificial results with new reflexes which he described in
1913. He states that the nervous system besides the primitive function
of reproducing innate reflexes, possesses another prime function-namely
the formation of new reflexes; and that the living thing is enabled
to respond, by definite and suitable activities to agencies to which
it was formerly indifferent. His experiments on the formation of
“conditional reflexes,” as he calls them rather than “acquired” as
opposed to “innate,” are grouped around the feeding of the animal
and mainly deal with the salivary glands, because they are in direct
connection with the external world and their reactions are simply and
easily observed. An indifferent stimulus is chosen for the reflexes
which it is desired to build up, and this is applied at the same time
as food or acid is introduced in the mouth. After a few sittings it
is found that this indifferent stimulus _alone_ is now capable of
calling forth a secretion of saliva. “The conditional reflex has been
formed; the formerly indifferent stimulus has now found a path to the
requisite part of the central nervous system. The reflex-arc has now
a different afferent neurone.” He gives a good example of this in the
result of the application of painful stimuli by a strong electrical
current to the skin, systematically accompanying each feeding of the
animal. He finds that the strongest electrical stimuli applied to the
skin give rise merely to the “feeding reaction,” that is, the secretion
of saliva, and no indications of any fright or pain appear. “The skin
of a dog can be subjected to cutting, pinching or burning, and the
only result we shall obtain will be the manifestation of what, judging
from our own experience, we should call the symptoms of the keenest
appetite; the animal follows the experimenter about, licks himself,
and saliva flows in abundance.” This, it must be remembered, occurs in
the absence of the offer or sight of food, _at the time in question_.
He adds: “In this way we have been able to divert the impulses from
one path to another according to the conditions, and we cannot avoid
the conclusion that the diversion of an impulse from one path to
another represents one of the most important functions of the highest
parts of the central nervous system.” The presence of certain special
conditions, he points out, causes the indifferent stimulus, which would
otherwise be dispersed in the higher centres, to be directed to a
particular focus, and _eventually to lay down for itself a path to that
part_. A very interesting detail of such a building of a new reflex is
that “the stimuli from which the new reflex is to be worked out shall
be rigidly isolated.” Therefore to avoid any interference with the
certainty of the experiment, such matters as a personal bodily odour
or kind of movement, or even such a slight fact as a change in the
mode of breathing familiar to the dog on the part of the experimenter,
has in the latest experiments been removed by the application of the
stimuli by mechanical devices worked from another room, with results
similar to the earlier ones. Conditional reflexes can also be obtained
from stimuli arising from the locomotor apparatus, as the joints,
eliminating the stimuli arising from the skin. Also certain parts of
the frontal lobes were extirpated and “when one part is extirpated
the reflex is obtained from the flexion of the joint, but not from
the skin; if a different part be removed we can get the skin-reflex,
but not the reflex from the joint.” He extirpated in one case the
greater portion of the posterior part of the brain and the dog lived
for several years after this in complete health. It was found easy to
obtain a conditional reflex for various intensities of illumination,
also for sound, and even a fine differentiation of tones. In another
dog the anterior half of the brain was removed and all the reflexes
before worked out in this animal disappeared, and yet in this helpless
condition of the dog he could train it to give that response of the
salivary glands which he called the “water-reflex,” in which first of
all an irritating acid was introduced into the mouth and the subsequent
administration of water provoked an abundant secretion of saliva which
does not occur when water is poured into the mouth of a normal dog.
This was confirmed in another example in which alone the centre for
smell had been spared, and yet it was possible in it to train the
smell-reflexes also. I add one striking sentence from Pawlow’s address
which, though an opinion, must be received with the respect it deserves
from such a source. “It is perhaps not rash to think that some of the
newly-formed conditional reflexes can be transmitted hereditarily and
become unconditional thereby.”
Indirect Evidence.
From these limited but cogent pieces of evidence I turn to the
larger but confirmatory lines of indirect evidence and inference, of
which such works as those of Professors Sherrington, Bayliss, and
Starling, the notable address of Professor Macdonald at Portsmouth
in 1911, as well as the recent work of Professor Woods Jones on
Arboreal Man, are full. Indeed if the construction of new reflexes
and reflex-arcs in organic evolution “forged by an incident of use”
as Professor Macdonald puts it, were expunged from these works, their
treatment of the physiology of the central nervous system of higher
animals would be emasculated, to say the least of it. And yet not
one of these eminent men is writing _ad hoc_, or for the confusion
of Weismann and his followers. At this point it may perhaps gain for
the remaining pages a little more consideration from opponents if I
give a few quotations from these writers in support of the foregoing
statement--perhaps the breeze of authority may then carry my little
bark a little further on its perilous voyage. Professor Sherrington
remarks on the first page of his well known work, in reference to the
cell-theory, “with the progress of natural knowledge, biology has
passed beyond the confines of the study of merely visible form, and
is turning more and more to the subtle and deeper sciences that are
branches of energetics. The cell-theory and the doctrine of evolution
find their scope more and more, therefore, in the problems of function,
and have become more and more identified with the aim and incorporated
among the methods of physiology.” Again, “Mere experience can apart
from reason mould nervous reactions in so far as they are plastic.
The ‘bahnung’ (or facilitation) of a reflex exhibits this in germ.”
He uses more than once the pregnant phrase, “The canalizing force of
habit”; again, “Progress of knowledge in regard to the nervous system
has been indissolubly linked with the determination of function in
it.” Speaking of the receptive-field he says of the central nervous
system, “To analyse its action we turn to the receptor organs, for to
them is traceable the initiation of the reactions of the centres”;
of the extero-ceptive field he says, “facing outwards on the general
environment it feels and has felt for countless ages the full stream of
the varied agencies for ever pouring upon it from the external world,”
page 20, and “each animal has experience only of those qualities of
the environment which as stimuli excite its receptors, it analyses
its environment in terms of them exclusively. The integration of the
animal associated with these leading segments can be briefly with
partial justice expressed by saying that the rest of the animal, so far
as its motor machinery goes, is but the servant, of them. Volitional
movements can certainly become involuntary, and conversely, involuntary
movements can sometimes be brought under the subjection of the will.
From this subjection it is but a short step to the acquisition of
co-ordinations which express themselves as movements newly acquired by
the individual,” and, “The integrating power of the nervous system
has, in fact, in the higher animal more than in the lower, constructed
from a mere collection of organs and segments a functional unity, an
individual of more perfected solidarity,” also “a single momentary
shock produces in the nervous arc a facilitating influence on a
subsequent stimulus applied even 1400σ later.” I will give but one more
statement from this work which seems to tell against my humble position
of initiative in evolution. Professor Sherrington says at the end of
his book, speaking of the adjustments of nervous reactions in the
lifetime of the individual: “These adjustments though not transmitted
to the offspring yet in higher animals form the most potent internal
condition for enabling the species to maintain and increase in sum
its dominance over the environment in which it is immersed.” A little
care in reading the foregoing chapters will show that this in no way
contradicts the views expressed.
Facilitation.
From Professor Starling’s Principles of Human Physiology I may again
quote part of his account of Facilitation or “Bahnung.” “When an
impulse has passed through a certain set of neurones to the exclusion
of others it will tend, other things being equal, to take the same
course on a future occasion, and each time it traverses this path the
resistance in the path will be smaller. Education is the laying down
of nerve-channels in the central nervous system, while still plastic,
by the process of ‘Bahnung’ along fit paths combined with inhibition
(by pain) in the other unfit paths. Memory itself has the process of
facilitation for its neural basis,” again, “stimulation of one anterior
root produces no definite movement of a group of muscles, but partial
contraction of a number of muscles which do not normally contract
simultaneously. Thus, stimulation of a sensory nerve may provoke either
flexion or extension of a limb, not both simultaneously. Stimulation
of the motor roots will cause simultaneous contraction of both flexor
and extensor muscles. It is _this subordination of morphological to
physiological arrangements_ in the limbs which has necessitated the
foundation of limb-plexuses.” (Italics not in the original). Professor
Graham Kerr in his work on Embryology before mentioned says: “In early
stages of Evolution, whether phylogenetic or ontogenetic, we may take
it that vital impulses flitted hither and thither in an indefinite
manner within the living substance and that one of the features of
progressive evolution has been the gradual more and more precise
definition of the pathways of particular types of impulse, as well as
the transmitting and receiving centres between which they pass. We may
then regard the appearance of neuro-fibrils within the protoplasmic
rudiment of the nerve-trunk as the coming into view of tracks, along
which, owing to their high conductivity, nerve-impulses are repeatedly
passing. It may be that as each successive passer-by causes a
jungle-pathway to become more clearly defined so each passing impulse
makes the way easier for its successors and makes it less likely for
them to stray into the surrounding substance” (p. 112).
Professor Macdonald, in the Portsmouth address referred to, speaking of
the states of the cells under excitation, rest, and inhibition, says
“_excitation_ is associated with an increase in pressure of certain
particles within the cells; in _rest_ these particles are in their
normal quantity and have their normal number. During _inhibition_ they
are decreased in number or have a retarded motion. Thus it happens
that the excited cell tends to grow in size, on the other hand the
inhibited cell tends to diminish, and the resting cell to remain
unaltered in the nervous system. Structure is everywhere the outcome
of function.” Speaking of the relationship of parts within the nervous
system, “In so far as it is fixed, it is a sign of the orderly action
of circumstance upon the structures of the body, and the result rather
than the cause of the monotony of existence. I hold it as probable
that all the individual structures of the nervous system, and so in
the brain, have just so much difference from one another in size and
shape and in function as is the outcome of that measure of physical
experience to which each one of them has been subjected; and that the
physiological function of each one of them is of the simplest kind.
The magnificent utility of the whole system, where the individual
units have such simplicity, is due to the physically developed
peculiarities of their arrangement in relation to one another, and
to the receptive surfaces and motor-organs of the body.” As to the
lens-system of the eyeball he remarks, “Surely there is no escape from
the statement that either external agency cognisant of light, or light
itself has formed and developed to such a state of perfection this
purely optical mechanism, and that natural selection can have done no
more than _assist_ in this process.” He applies the same conclusion
to the formation of the sound-conducting and resonant portion of the
ear as well as the semi-circular canals and to the cerebellum. These
statements are not strictly associated with this chapter but bear by
analogy very strongly on the matter at issue. Indeed the whole of this
address might be utilised by a junior counsel for Lamarck if he rested
alone on the authority of a leading physiologist. The same may be said
of the anatomist whose _Arboreal Man_ has attracted so much attention.
Speaking of the arboreal habit in the phylogenetic history of mammals
he asks the question, “How did this factor enable that particular stock
to acquire supremacy?” and says that it will be answered as far as it
is possible, by the study of the influence of the arboreal habit upon
the animal body; which may be put in another way as the production of
reflex-arcs suited thereto (p. 3.) Of the muscle groups of fore and
hind limbs he says, “With a simple arrangement of anatomical parts
a slight shifting of muscular origins has turned a perfectly mobile
second segment into a supporting segment constructed upon very simple
lines: that these changes are those produced by the demands of support
from the hind-limbs in tree-climbing seems obvious” (p. 6); of the
position of uprightness upon a flexed thigh of an arboreal man, “It is
tree-climbing which makes this posture a possibility” (p. 63). “But it
is not to be doubted that the underlying principle is clear enough,
that the arboreal habit develops the specialised and opposable thumb
and big toe” (p. 71). “Even before the power of grasp is developed,
we may imagine the dawn stages of educational advances initiated by
hand-touch” (p. 159). “Tactile impressions gained through the hand are
therefore perpetually streaming into the brain of an arboreal animal
and new avenues of learning about its surroundings are being opened up
as additions to the olfactory and snout-tactile routes” (p. 160). He
asks also the pertinent question, and says at least a partial answer
to it can be given, “Did the cerebral advance create the physical
adaptations, or did the physical adaptations make possible a cerebral
advance?” (p. 196). Two more statements from this chapter show what
the answer to this question from the _anatomist_ would be--“and again
in the evolutionary story we are forced back to consider a combination
of seemingly trivial, and apparently chance associations: in this case
the dawning possibilities of neo-pallial developments combined with
the physical adaptations _due directly to environmental influences_”
(p. 198). I have ventured to underline this passage.
I regret the necessary length of these quotations but, on account of
them, can the better be suffered to finish this study, when I briefly
consider certain well-known nervous reactions in the cat and dog as
to their probable origin. It would be a highly interesting thing to
hear an exposition by an expert of all the reflexes and reflex-arcs of
such a system as those which in a cat, dog, ape, or man are concerned
with the passage of a morsel of food from the mouth through all its
chequered and varied career till it undergoes metabolism and excretion,
but I could not do it if I would, and would not here if I could,
because of their fundamental fixed and innate character, and I think
it simpler and safer to refer to such minor reflex-arcs as those which
govern the scratch-reflex in a dog, the pinna reflexes in a cat, and a
few smaller ones, on the principle of _ex uno disce omnes_. Such minor
nerve-mechanisms as these in a pair of well-known domesticated animals
will suffice for evidence on behalf of initiative in evolution.
The Scratch Reflex.
The scratch-reflex in the dog, which like the tendon-reflex in man was
in my youth a subject for schoolboy tricks, has received a vast amount
of attention and research from physiologists to whom it has brought
valuable fruit. It is a familiar phenomenon in a familiar friend of
man. There is a saddle-shaped area on the back of the dog over which
it was found empirically that even a light stimulus when applied
rhythmically, produces the “scalptor-reflex” or a reflex rhythmical
action of the flexor muscles of the leg on the same side, calculated to
remove the irritating causes of the stimulus. This includes a series
of receptors in the skin leading to a spinal segment in the region of
the shoulder, a long neurone in the cord, then a motor neurone, the
axon from which activates the flexor muscles of the leg and produces
scratching. It is described as an efferent arc from receptor to the
motor neurone, from which the Final Common Path supplies the motor
apparatus or effector. Professor Sherrington says that in this reflex
a single stimulus which is far below threshold intensity is found
on its fortieth repetition and nearly four seconds after its first
application to become effective and provoke the reflex and that its
frequency is about 4.5 per second. The reflex movement remains rhythmic
and clonic under the strongest as under weaker stimulation. When it is
easily elicitable the scratch-reflex can be evoked by various forms
of electrical as well as mechanical stimulation, but, when not easily
elicitable, electrical stimulation fails whereas rubbing or other
mechanical forms of stimuli still evoke it, though less vigorously than
usual. This reflex can also be set aside by the “nociceptive arc from
the homonymous foot” or, in other words, a nocuous stimulus to the leg
of that side produces “interferences which amounts to inhibition.”
Empirically it is easy to notice also that if the “scalptor-reflex”
can be elicited on both sides of the body, the dog when standing will
momentarily lose the power in the hind legs.
_Note._--The rhythm of this reflex act is so special even to the
layman that lately I had a singular confirmation of its stereotyped
character, when lying awake at night and being puzzled by a curious
rhythmical scratching sound coming from my next door neighbour’s back
yard. It might have been taken by a wakeful person for some mechanical
work on the part of a burglar, but after listening repeatedly to the
apparently familiar sound I found that it came from the kennel of a fox
terrier kept by my neighbour.
Purposes of Reflexes.
All reflexes being purposive this particular innate reflex is
acknowledged to have for its purpose the grooming or cleaning of the
skin over its hereditary territory. This introduces its connection
with initiative here propounded, and the justification for its
introduction is contained in Professor Sherrington’s statement that
“In the analysis of the animal’s life as a machine in action there can
be split off from its total behaviour fractional pieces which may be
treated conveniently, though artificially, apart, and among these are
the reflexes we have been attempting to decipher”--scratch-reflexes and
others. There seems to be no reason for the existence and stereotyped
character of this reflex except the need or rather the desire (if
one may use a convenient but inaccurate term) on the part of the dog
to remove an irritant which disturbs its comfort when at rest. Some
“minor horrors,” probably fleas moving across the skin-receptive
field of its shoulder and back, must be assumed to be the irritant in
question. This touches the great question of the initiative of this
remarkable reflex, which seems more fixed and powerful in the dog as
we know him than that other reflex which leads him to turn tail and
flee immediately he sees a boy stoop down as if to pick up a stone. I
dare say a clever advocate on the opposite side might impress a jury by
building up a case under which an adaptation to a protective need would
be conceived as responsible for the rapid flight at the sight of the
threatening attitude of the boy. Such a reconstruction is not required,
for it is perfectly clear that in the history of the domesticated
dog the selection of such an adapted reflex could have no place. The
survival-value of this reflex would be nil, for the number of dogs
killed by a stone or maimed for life would be so negligible that the
production of a specialised reflex for the purpose by selection or
survival of the fittest would not arise. Obviously the danger would
be intermittent and rare; and dead dogs tell no tales. On the other
hand it would be highly unpleasant for dogs to be hit by stones and
educability would lead them to avoid the stooping attitude associated
with missiles.
We are told on high authority that not education but educability
is transmissible, and yet this humble reflex appears in very young
dogs that could hardly if ever have known the impact of a stone.
Incidentally we are compelled to remember how in past battles of our
youth the aim both of “ourselves and the enemy” was deplorably poor,
and not from want of practice. This school-boy-stone reflex is either
an example of educational effects transmitted or of a minute bit of the
unpacking of an original complexity which it would require the brain of
a de Quincey to work out. But if we suppose the initial stages of such
a stimulus as the occasional impact of a stone in many generations to
be slowly ingrained in the skin-receptors, reflex-arcs and receptors we
do not need opium either for the acceptance of orthodox dogma or to aid
us in the Mendelian alternative to a very simple ideal construction.
This digression bears on the initiative of the more important
scratch-reflex, and it is profitable to ask “are not both of these
reflexes in dogs examples of Evolution of the Indifferent?” Is it
possible to imagine that from its inception to its fully-formed state,
with a specialised territory of skin-receptors accurately mapped
out, with receptor neurones, reflex-arcs and adapted effectors, this
scratch-reflex can have arisen through Germinal Selection or selective
processes within the germ? At no stage can anything more than a
contribution to more or less comfort to the animal be held to result
from its operation. It is strangely reminiscent of the proceedings
of an elderly man after lunch on a hot day when he protects his head
against house-flies with a handkerchief. I am aware that it is but one
of a large number of reflexes produced for the purpose of grooming
the trunk head or limbs of animals as low down in the scale as the
house-fly or grasshopper, many of which were beautifully described
a few years ago by Miss Frances Pitt in the _National Review_ in an
article dealing with small mammals, chiefly rodents. But I have availed
myself here as elsewhere, of the liberty of doing what Professor
Sherrington says we may do, and consider this scratch-reflex as
split off from the rest of the animal’s behaviour for the purpose of
analysis. He also says in discussing the subject of parasites moving
across the receptive surface of the skin that the ulterior purpose
may be the removal of what “would confuse its function as a receptive
surface to more significant environmental stimuli.” This statement is
hypothetical and the problem obscure; but at any rate we know this that
the removal of the parasite must conduce to the greater comfort of the
dog without any more recondite purpose. The one suggested by Professor
Sherrington would in some possible but very vague manner be referable
to selection, but, whether the suggestion be valid or not, it is almost
impossible to suppose that a saddle-shaped area of the kind described
could be under the guidance of selection. The law of Parcimony forbids.
There is a close similarity between this saddle-shaped area in the dog
and that on the cow’s trunk described in Chapter X. It is difficult
to believe that from man downwards to grasshoppers relief from mild
irritating causes such as this is not enjoyable to the particular
animal, and yet indifferent altogether as to its survival in the
struggles of life for food and mates. The “scalptor-reflex” only
reaches the limits of the receptive field of the scratch-reflex and it
is contrary to observed facts that parasites confine their depredations
just to the region where the formidable scalptor-reflex can reach. The
wicked flea knows better than that. The initiative of this reflex can
well be pictured as taking place in domesticated dogs and their wild
ancestors whose habitats in prehistoric times were probably infested
with these irritants to such a degree that no modern mind can conceive,
and the adequate stimuli, leading to receptors after ages of impact and
consequent hammering out pathways through certain reflex-arcs until
the required weapons of offence or effectors were organised into a
_defensive-offensive system_--were there in profusion. But a great and
fundamental principle of the evolutionary process such as Selection
is not honoured by being dragged in, even for forensic purposes,
to account for results which owe to the search for comfort their
perfection of organisation. I have personally seen in some professional
invalids of the softer sex nearly as perfect adaptations to their
comfort which in no way contributed to their length of life. This may
be put aside as irrelevant but it is at least suggestive.
I submit the statement as to the scratch-reflex in the dog that from
beginning to end it is an _indifferent_ mechanism and the probability
is immense that its initial stages were governed alone by repeated
stimuli from parasites which produced receptors, conducting fibres
afferent neurones and efferent neurones, leading into the Final
Common Path controlling the flexors of the hind limb. It would then
come under the Law of Subjective or Hedonic Selection formulated by
Professor Stout in the words: “Lines of action, if and so far as they
are unsuccessful, tend to be discontinued or varied; and those which
prove successful to be maintained. There is a constant tending to
persist in those movements and motor attitudes which yield satisfactory
experiences, and to renew them when similar conditions recur; on the
other hand those movements and attitudes which yield unsatisfactory
experiences tend to be discontinued at the time of their occurrence,
and to be suppressed on subsequent similar occasions.”
In this connection a statement from Professor McDougall’s work may be
advantageously quoted. He says that “It is characteristic of those
(arcs) of the higher or third level that their organisation, their
interconnections, by means of which the simpler neural systems of
great complexity, is _congenitally determined in a very partial degree
only_, and is principally determined in each individual by the course
of its experience. The arcs of the higher level thus constitute the
physiological basis or condition of docility, the power of learning by
experience.”[88] (My italics)
[88] _Op. cit._ p. 21.
Scratch Reflex of the Cat.
There is a notable difference between the scratch-reflex of the dog
and that of the cat, especially as to the site of its receptive-field.
That of the dog has been referred to, but it appears to be generally
accepted that the cat has no such saddle-shaped or indeed other area of
skin receptive-field on its back or flanks. I have repeatedly tried by
various mechanical stimuli, applied both irregularly and rhythmically,
to evoke a scratch-reflex in a cat, young or adult, on the surface
corresponding to that of the dog, and have found no response. This
has been tried both when the animal was awake and when asleep. But
the receptive field of the cat’s scratch-reflex has received careful
and elaborate attention, which is described in a paper by Professor
Sherrington in the _Journal of Physiology_, Vol. LI. No. 6. By means of
delicate stimuli, mechanical and electrical in a decerebrate cat, the
receptive-field of the scratch-reflex has been accurately delineated
in the pinna, and several other pure reflexes have been obtained.
These are protective of the pinna; some, the retraction and folding
reflexes seem directed against irritant touches, _e.g._ the settling
of fleas--or against exposure to injury in fighting; others, the cover
and head-shake and scratch-reflexes against the ingress of foreign
matter, such as dust, water, insects, into the meatus and ampulla. The
threshold for their elicitation is extremely low, that is to say, they
require very gentle stimuli to evoke them, while with the exception of
the scratch-reflex they are elicited with difficulty and uncertainty
_by electrical stimuli_ (My italics) to which the animal has been
subjected in the course of its total experience. He adds that the
pinnal reflexes are readily obtained in the normal animal, and I may
allude here to some small observations I made on a normal young cat
during profound sleep, recorded in _Nature_, Vol. 106, Sept. 2, 1920.
Light mechanical stimuli, applied during this state of deep sleep to
the internal surface of the pinna, especially close to the meatus,
produced first, twitching of the facial muscles on the same side;
second, as this ceased the fore foot was moved irregularly towards the
ear, and third, as this ceased a rhythmical scratching action of the
hind foot took its place, the rate of which seemed to be exactly the
same as that of the scratch-reflex in the dog evoked from stimulation
of the flank and back. I had not then, unfortunately read more than
an abstract of the above paper, but if the full account be followed
it will be seen that the various “territories” belonging to all the
former-reflexes are now known as well as the frontiers of a European
Kingdom. All I was able to do with this unusual opportunity of a heavy
sleep in a normal young cat was to verify more roughly Professor
Sherrington’s observations and slightly to extend them _in respect of a
sleeping animal_.
In the course of these observations on a young cat I examined the
various regions of the back and flanks with mechanical stimuli of
different degrees of strength. These were applied during sleep and I
found that it was more often during a moderate than a light or deep
sleep that the following results were shown--chiefly under the stronger
stimuli the tail was raised sharply and swept in a circular way, and
this would be repeated according as the stimulus was applied; but at
the same time there was shown a strong, irregular twitching along the
flank, extending forwards to a point near the level of the shoulder.
This latter reflex would appear to be a reaction on the part of the
panniculus carnosus. Both the reflex of the muscles of the tail
and this of the flanks appear to be connected in their origin with
movements of parasites in their respective territories.
In considering the scratch-reflex in the cat a subtle bit of adjustment
is found. That coarse and simple scratching of its ear, which we see
so often in the cat, must have often astonished us for its vigour and
yet its bloodless character. This action is of course a purposeful
one, for it goes on when the animal is awake. Here if anywhere this
profoundly hedonistic animal shows that for it the laws of comfort
are its laws of conduct. It is clear that there may be two processes
or conditions involved in its bloodless violence. On the one hand the
reflex retractile mechanism of the claws may be kept in abeyance by
another reaction which is pre-potent; on the other, it is a fact that
the hind foot in the cat is furnished with claws which are much blunter
than those of the fore foot. As far as I have been able to examine cats
of different ages I have found the claws of the hind foot more like
the blunt claws of a dog than the familiar sharp claws of the Felidæ.
So in the violent scratching referred to there may be a double reason
associated in the process. As to the difference in the sharpness of the
fore and hind claws it would appear to be remarkably like a transmitted
bit of adaptation initiated and kept in being by use and habit in
progression, for the hind foot in such animals as the cat has a larger
share in this action than the fore foot. But here it is difficult as so
often to assign to selection its possible share of the adjustment.
Certain minor but persistent reflexes may be briefly mentioned in
support of this side of the evolutionary process. In the dog and cat,
as we know them, the action of the muscles of the tail by which it is
elevated during the act of defæcation is very suggestive of a reflex
acquired by a very small degree of physical comfort and repeated in
countless individuals, wild and domesticated. I have seen not only this
but a few small scratches made by a cat before defæcation in a kitten
as young as three weeks old. It is also mentioned in illustration of a
vestigial character that a horse will paw the ground with no immediate
apparent object, the act being derived from ancestors which thus
cleared away snow from the ground. This is claimed, doubtfully I think,
as a vestige of a formerly _useful_ habit but seems more probably to
be one of these indifferent reflexes connected with comfort than with
survival-value.
It will be observed that in this branch of the case for Lamarck _v._
Weismann the indirect evidence from inference far exceeds in amount
that of direct experimental evidence, but from the nature of the
problem under consideration this could not be otherwise.
If we may again look back in thought over the long series of animals,
from man downwards, we shall picture those of the spinal level
striving (with apologies for the use of an anthropomorphic word) to
reach the sensory level and finding out the fact that few there be
that enter therein. Again we see in vision the higher creatures of
the sensory level reaching forwards to the strait paths of primate
existence, and again finding the difficulty of self-advancement that
their predecessors found. We see the elect few of these, by a happy
combination of nature and nurture, uprearing to glory and honour the
primate stock with its culmination in man. A long vista indeed and a
vision, but assuredly no mere figment of the imagination, as some of
the slender facts and arguments here would seem to show. With Professor
Bateson we personify Nature in the story, with her wonted coyness
betraying the fact that though she is stern she has her tolerant
moods; that she allows her children, even that “insurgent son” who
calls himself Homo Sapiens, a genial liberty to frame new reflex-arcs
which make for his enjoyment of life in indifferent fields, and _that
the great neural process of Facilitation is the leading factor in
their constructions and probably also in more deeply-based systems of
sensori-motor arcs_.
SUMMARY.
Though it be true that _dolus latet in generalibus_, it is a more
important truth that “without premature generalisations the true
generalisation would never be arrived at.”[89]
[89] Herbert Spencer, _Essays_, II, 57.
Therefore I conclude:--
1. That Plasto-diēthēsis, or the moulding and sifting processes
experienced by organisms, represents the beginning and end of higher
animal evolution; and that its wide hyphen stands for the provinces
where Mendelism, Mutationism, Tetraplasty, Orthogenesis, and the
dynamical work of growth on Form, as well as other factors yet to be
discovered, can range at large.
2. That personal selection is the leading form of that process in
higher animals, whereas among Invertebrates, especially unicellular
forms, selection of groups is the rule.
3. That Initiative in animal evolution comes by stimulation,
excitation, and response in new conditions, and is followed by
repetition of these phenomena until they result in structural
modifications, transmitted and directed by selection and the laws
of genetics--a series of events which agree with Neo-Lamarckian
principles.
4. That undesigned experiments in the arrangement of the Mammalian
hair, and the production of new bursæ, as well as the designed
experiments of Pawlow, support the foregoing claims, with which agree
the converging facts of--varieties of epidermis, arrangement of the
papillary ridges, flexures of the palm and sole, the formation of the
plantar arch, the origin of certain muscles, the innervation of the
human skin, and the building of reflex-arcs.
5. That there is a large place in higher animals for the Evolution of
the Indifferent through the action of use and habit.
6. That the position for Initiative in Evolution here advanced is no
bar to unlimited research.
INDEX.
Adami, Professor. “Medical Contributions to the Study of Evolution,”
21.
Ancestry, primate, 235, 236.
Anthropology, 4.
Ape: Arrangement of hair on forearm of, 43.
----Papillary ridges on hand and foot of, 164.
----Bursæ of, 184–186.
----Muscles of, 213, 214.
Artists, Evidence from, 66.
Ass: Hair-patterns of, 82.
Baboon, Chacma, papillary ridges on hand and foot of, 165, 166.
Bartholinus, Erasmus, 126.
Bateson, Professor, 9, 20, 22, 33, 149, 255.
----“Materials for the Study of Variation,” 9–13, 22, 210.
Bayliss, Professor, 244.
Bear, Parti-coloured (_Æluropus melanoleucus_): Hair-patterns of,
121, 122.
Beddard, Mr., 118.
----“Animal Colouration,” 206.
Bell, Sir Charles, 205.
Bergson, 205.
Bongo (_Tragelaphus euryceros_): Hair-patterns of, 118.
Bonney, Professor. “The Story of Our Planet,” 3.
Bower, Professor, 21.
Brooks, Professor, W. K., 20, 202.
Bursæ, description of, 179, 180.
----Human, enumerated, 180–183.
----Experiments as to, 186–190.
Canidæ: Hair-patterns of, 98–102.
Capybara, epidermis of, 151.
Chimpanzee, papillary ridges on hand and foot of, 164, 167, 168, 176.
----Bursæ of, 184, 185.
Clark, Sir Andrew, 30.
Cold and warmth sensations of human skin, 220–230.
Coote, Captain, 194.
Correlation, 28.
Correns, 11.
Cow, hair and habits of, 87–91.
----Fly-shaker muscles of, 90, 211, 212.
Crime, detection of a, 5.
Cunningham, J. T., 21.
Darwin, 1, 2, 15, 35, 39, 40, 139, 145, 147, 239.
----“Origin of Species,” 2, 8.
----“Descent of Man,” 2.
----Three Blows to, 9.
----On human eyebrows, 64, 65.
Darwin, Sir Francis, 20, 21.
----On Mnemonic theory of Heredity, 20.
Darwinism, 9, 15, 25, 145.
Dendy, Professor. “Outlines of Evolutionary Biology,” 21.
de Vries, 11, 24, 27, 145, 190.
Dog: Arrangement of hair of, 27, 28, 34, 100–102.
----Habits of, 98, 99.
Dyer, Professor Thiselton, 210.
Earth Wolf, epidermis of, 150.
Echidna, epidermis of, 151.
Elliott, Professor Scott, 98, 126.
----“Prehistoric Man and his Story,” 43, 47, 226.
Environments, Discontinuous, 31–33.
Epidermis: Varieties of, found in mammals, 145.
----Stimuli and response, 145–153.
Eyebrows, hairs of human, 64–73.
----Interpreted by wrinkles, 67.
Facilitation, 240, 246–248.
Felidæ: Hair-patterns of, 92–97.
----Snout of, 94.
Flexures of hand and foot, description of, 170–172.
----Chief types of, 172.
----Meaning of, 173–177.
Foot of Man, 155, 156.
----Papillary ridges on, 159, 160.
----Flexures of, 176, 177.
Foot of Man, Plantar arch of, 192–194.
----Muscles of, 214–217.
Forearm, arrangement of hair on, 41.
Galton, 157; On chiromantic creases, 170.
Galvani, 126.
Geikie, Sir Archibald, 3.
Genealogy, 4.
Germinal Selection, 19, 20.
Gibbon, flexures of foot of, 176.
----Bursæ of, 185.
Gibbon, Hainan, papillary ridges on hand and foot of, 164, 165.
Giraffe: Habits of, 115.
----Hair-patterns of, 117.
Gorilla, papillary ridges on hand and foot of, 164.
Haeckel: Pithecoid Ancestors of Man, 1.
Hair-direction, causation of, 140–144.
----Summary of conclusions with regard to, 141.
----Phenomena of, 37, 38.
----Experimental Inquiry into, 125, 126.
----Steps of Inquiry into, 40, 124, 125.
Hair-pattern, Dynamics of, 44, 45, 46, 50.
Hand of Man, 155, 156.
----Papillary ridges on, 157–159.
----Flexures of, 176, 177.
----Muscles of, 214–217.
Harris, Dr. H. Wilder, 147, 154.
Harris, Mrs. Wilder. _See_ Whipple, Miss Inez.
Hartmann, 213.
Hedgehog, epidermis of, 152.
----Papillary ridges on hand and foot of, 162, 163, 166.
----Flexures on hand and foot of, 173.
Hepburn, Dr., 148, 159, 162.
Heredity, Mnemonic theory of, 20.
Herschel, Sir John, 126.
Hill, Professor Leonard, 224.
Historian a biologist, 2.
Horse: Arrangement of hair on side of neck of, 51–63.
----Habits of, 75.
----Hair-patterns of, 75–82.
----Compared with Zebra, 83–85.
----Effect of harness upon hair of, 126–136.
----Fly-shaker muscles of, 211.
Howes, G. B., 12.
Hutchinson, Professor Jonathan, 188.
Hutton, 3.
Huxley, 5, 8, 126, 192, 200, 217.
Insectivores, 237, 238.
Jackson, Hughlings, 241.
Jevons, 124, 125, 126, 140.
Johnston, Sir H. H., 96, 201.
Jones, Professor Wood, 230.
----“Arboreal Man,” 195, 245, 248.
Kammerer, 21.
Keith, Professor, 112, 188, 189, 190, 195, 196, 208, 215, 216, 217.
----On functions of platysma, 113.
Kerr, Professor Graham, 224.
----On Embryology, 246, 247.
Kiang (Thibetan Wild Ass): Hair-patterns of, 119.
Kinkajou, epidermis of, 153.
Kropotkin, Prince, 21.
Lamarck, 13, 21, 22, 33, 35, 145, 147, 247, 255.
Lamarckian hypothesis of organic evolution, 19, 20, 22, 24, 25, 26,
28, 30, 31, 138, 205.
Lankester, Sir E. Ray, 20, 23, 45, 141, 190, 204.
Lemur: Arrangement of hair on forearm of, 43.
----Hair-pattern of, 46.
----Papillary ridges on foot of, 161, 162, 164, 165.
----Black-headed, epidermis of, 153.
----Ring-tailed, epidermis of, 153.
----Flexures of foot of, 176.
Lion: Hair-patterns of, 92–97, 207.
Livingstone, 92.
Llama: Hair-patterns of, 119, 120.
Loris, Slow: epidermis of, 154, 155.
----Papillary ridges on foot of, 161, 166.
Lydekker, 86, 92, 94, 115, 118, 119, 168, 195.
Lyell, 3, 178, 192.
----“Principles of Geology,” 3, 46.
Macacus, flexures of hand and foot of, 176.
Macalister, 215, 217.
McBride, Professor, 21.
Macdonald, Professor, 190, 244, 245, 247.
McDougall, Professor: On Physiological Psychology, 24, 25, 225, 253.
MacEwen, Sir W., 188.
McTaggart, Dr., 142.
Malthus, 2, 15.
Malus, 126.
Mammals, palms and soles of, 150–153.
Man: hair and habits of, 103.
----Arrangement of hair on back of, 104.
----Passive habits of, 106, 107.
----Arrangement of hair on chest of, 108, 109.
----Palm and sole of, 155, 156.
----Papillary ridges on hand of, 157–159.
----Papillary ridges on foot of, 159, 160.
----Flexures of palm and sole of, 176, 177.
----Plantar arch of, 192–194.
----Muscles of hand and foot of, 214–217.
----Changes in habits of, 234, 235.
Marmoset, Papillary ridges on foot of, 161.
Mendel, 11, 15, 26, 145, 190.
Mercier, Dr.: On Causation, 141, 142.
Mill, John Stuart, 141, 142.
Mole, epidermis of, 150.
Monkey, papillary ridges on hand and foot of, 164.
Mule: Hair-patterns of, 82.
Murphy, Dr. John B., 189.
Muscles: Anatomists’ views of, 201, 202.
----Initiative in, 202, 203.
----New, 205.
----Unstriped, 205, 206.
----Facial, of expression, 207–209.
----Fly-shaker, 210–212.
----Skeletal, 212, 213.
----Skeletal, of Primates, 213, 214.
Neural phenomena, 239.
Nervous System: Some aspects of the, 223–225.
----Place of the, in Evolution, 238, 239.
----Raw materials of the, 240, 241.
----Integration of raw materials of the, 241, 242.
Oken, 126.
Ollier, 188.
Onager, Hair-patterns of, 82.
Opossum, American, epidermis of, 151.
----Azara’s, epidermis of, 153.
Orang, papillary ridges on hand and foot of, 164.
----Bursæ of, 185.
Organic Evolution, consideration of problems of, 24–28.
----Factors in, 27.
----Cross-roads in, 203–205.
Owen, Richard, 10.
Oxen: Hair-patterns of, 87–91.
Palm, skin of, 147–156.
----of Man, 155–156.
Papillary ridges, some undersigned experiments in, 166–169.
Paterson, Dr. C., 188.
Pearson, Professor Karl, 34, 141, 142.
Phalanger, epidermis of, 152.
Pitt, Miss Frances, 94, 95, 251.
Plantar arch, of man, 192–194.
----How it was built, 194, 195.
----Equipment of, 196, 197.
----Description of, 197–199.
Plasto-diēthēsis, 34, 145, 195.
Platysma, Struggles of the, 111–114.
Playfair, 3.
Pocock, Roger, 75.
Poincaré, Henri, 157.
----Principles of method, 36.
Porcupine, Canadian Tree, epidermis of, 151, 153.
Poulton, Professor: “Essays on Evolution,” 86.
Prescott’s “Conquest of Peru,” 120.
Pressure, Examples of the effects of, upon hair-direction, 127–136.
Primates, epidermis of, 153.
Rabbit, epidermis of, 151.
Records, Interpretation of, 110.
Reflex arches, formation of, 231.
----Some historical illustrations of, 231–234.
----Of Insects, 236, 237.
----Of Mollusca, 236, 237.
----Of Birds, 236, 237.
----Evidence of production of new, 242–246.
Reflexes: Stimuli of, 249–256.
----Scratch, of the dog, 249.
----Purposes of, 250–253.
----Scratch, of the cat, 253.
Rivers, Sources of, 4.
Romanes: 19, 39, 40, 145.
----On Weismann, 17, 18.
Roux, 19, 145.
Russell, The Hon. Bertrand, 142.
Russell, E. S. On Lamarck’s theory, 20.
Saint-Hilaire, Geoffrey, 10.
Sapajou, Brown, papillary ridges on hand and foot of, 165.
Schafer’s “Text Book of Physiology,” 219, 220, 226.
Scratch reflex; of the dog, 249.
----Of the cat, 253.
Selous, 92, 115, 118.
Sherrington, Professor, 218, 226, 229, 238, 244, 245, 249, 250, 251,
253, 254.
Skin, Human: Distribution of Touch Corpuscles, 219.
----Distribution of Touch Spots, 219.
----Distribution of Cold and Warmth Sensations, 220.
----Distribution of Cold and Warmth Spots, 220, 221.
----Stimuli of pressure, 222, 226–230.
----Stimuli of cold, 226–230.
----Stimuli of pain, 226–230.
----Stimuli of warmth, 226–230.
Sloth, Two-toed (_Cholæpus didactylus_): Hair-patterns of, 122, 123.
Smith, Dr. E. Barclay, 201, 216.
Sole, skin of, 147–156.
----Of Man, 155, 156.
Spencer, Herbert, 28, 177.
Squirrel, epidermis of, 152.
----Papillary ridges on hand and foot of, 162, 166.
----Flexures of hand and foot of, 175.
Squirrel-monkey, papillary ridges on foot of, 161.
----Flexures of foot of, 176.
Starling, Professor, 227, 244.
----On Facilitation, 240, 246.
Still-born children, subcutaneous bursæ of two, 183, 184.
Stimuli, 30, 31.
----Of touch, 219, 226–230.
----Of cold, 220, 226–230.
----Of warmth, 220, 226–230.
----Of pressure, 222, 226–230.
Stout, Professor, 252.
Summary of conclusions arrived at, 257, 258.
Thomson, Professor J. Arthur, 20, 22, 23, 24, 25, 28, 29, 34.
----On Heredity, 22.
Touch Corpuscles, 219, 227, 228.
Touch spots, 219, 225, 227, 228.
Tschermak, 11.
Ungulates, even-toed, 86–91.
----odd-toed, 74–85.
Vernon, Dr.: “Variations in Animals and Plants,” 28.
Vulpine phalanger, flexures of foot of, 173, 175.
Wallace, Professor, 2, 39, 40, 46, 145.
Weber’s Law, 222.
Weismann, 9, 11, 14, 16, 17, 18, 21, 22, 24, 25, 26, 86, 139, 177,
210, 245, 255.
----Twelve points, 15, 16.
Weismannism, 17, 18, 19, 26, 145.
Welton, Mr., 142.
Whipple, Miss Inez (Mrs. Wilder Harris), 154, 162.
----Criticism of “The Direction of Hair in Animals and Man,” 137–139.
Wolff, 189: “Law of Bone Transformation,” 205.
Young, Arthur, 143.
Zebra: Comparisons between horse and, 83, 84.
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