1 86 STRUCTURAL AND SYSTEMATIC ZOOLOGY 



The canines are often wanting in the mare. The horse 49 

 walks on the third finger arid toe. The metacarpals and 

 metatarsals are greatly elongated, so that the wrist and 

 heel are raised to the middle of the leg (Fig. 314). 

 The rhinoceros and tapir 50 each have three toes. The 

 first is distinguished by its very thick skin, the absence 

 of canines, and one or two horns on the nose. The 

 tapir has the four kinds of teeth, and a short proboscis. 

 The Even-toed Ungulates hog, hippopotamus, and 

 ruminants have two or four toes. The hog and hip- 

 popotamus have the four kinds of teeth (Fig. 232); and, 

 in the wild state, are vegetarian. The ruminants have 

 two toes on each foot, enveloped in hoofs which face 

 each other by a flat side, so that they appear to be a 

 single hoof split or "cloven." Usually there are also 

 two supplementary hoofs behind, but they do not ordi- 

 narily touch the ground. All chew the cud, and have a 

 complicated stomach (Fig. 254). They have incisors in 

 the lower jaw only, and these are apparently eight; but 

 the two outer ones are canines. 51 The molars are flat, 

 typical grinders. The dental formula of the ox is 



o o o o 



" 



3 



With few exceptions, as the camel, all ruminants have 

 horns, which are always in pairs. Those of the deer 

 are solid, bony, and deciduous ; those of the giraffe and 

 antelope are solid, horny, and permanent; in the goat, 

 sheep, and ox, they are hollow, horny, and permanent. 



The elephant, now nearly extinct, is characterized by 

 two upper incisors in the form of tusks, mainly com- 

 posed of dentine (ivory). In the extinct dinotherium 

 the tusks projected from the lower jaw ; and in the 

 mastodon, from both jaws. . Canines are wanting. The 

 molars are few and large, with transverse ridges (ele- 

 phant) or tubercles (mastodon). The cerebrum is large 



