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.