HABITS AND HAIR OF UNGULATES 81 



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 for- 

 wards, 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 ana- 

 tomist 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 



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