CH. Il] 



THE EXISTING EQUIDAE 



13 



little below the true hock joint and immediately over the 

 cuneiform bone (Figs. 1 — 4). The callosities near the knee and 

 hock are termed chestnuts or castors, and those under the fetlock 

 ergots. The chestnuts on the fore-legs of all Equidae are more 

 or less oval in form, those of ordinary domestic horses being 

 usually about 2 inches long. The hind chestnuts (which Equus 

 caballus almost alone of the family possesses) are somewhat 

 similar in shape to the fore ones, though a little smaller and 

 narrower (Fig. 1). 



The ergots in all members of 

 the genus are more or less round 

 (Figs. 5 — 10), and in ordinary 

 domestic horses are less than 

 a quarter of the size of the 

 chestnuts. As Prof. Ewart has 

 shown, the front chestnuts cor- 

 respond to the wrist pads, the 

 ergots to the middle portion of 

 the trilobed sole pad in the dog 

 and cat. Other zoologists^ hold 

 that the chestnuts are the re- 

 mains of scent glands, similar 

 to those found in some species 

 of deer and other animals. 



According to M. Sanson 

 the absence of the hind chest- 

 nuts is of frequent occurrence 

 among the horses and ponies 

 of North Africa, although they 

 are almost invariably present 



in ordinary breeds : in very rare instances there are no chest- 

 nuts on the fore-legs of domestic horses. Though ergots are 

 generally present, Captain Hayes has "noticed their frequent 



Fig. 1. Hind leg of Arab of coarse 

 type, with callosity like that of 

 Prejvalsky's horse. 



1 Sir W. H. Flower, The Horse, p. 170 (but he held that the ergot on the 

 hinder aspect of the horse's pastern appears to represent one of the pads, which 

 are still functional in the foot of the tapir). Mr K. W. Lydekker, F.K.S. (Proc. 

 Zool. Soc, 1903, pp. 199—203) has attempted not "so much to show what the 

 equine callosities represent," but rather " from palaeontological considerations 

 the improbability of their being vestigial foot-pads." 



