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.

Fig. 30.—Front view of horse show­ing pec­toral pattern A, B, C.

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.

Fig. 31.—Side-view of horse showing inguinal whorl, feathering and crest A, B, C, and axil­lary whorl, feather­ing and crest, G, H, I.

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.

Fig. 32.—Frontal region of horse with frontal whorl (a); feather­ing (b); crest (c).

Fig. 32A.—Muscles of the fronto-nasal region of the horse.

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.

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.

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.

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.