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.
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.