334 BRANCH CHORDATA 



and Burmese " |>ay high prices for the horns, tongues, and other efficacious 

 parts of the eastern rhinocerous, to be ground into medicinal powders." 1 



The horse (Eq'uidie) has the most complete geologic record of any living 

 animal. Fossil remains were found in the Eocene Epoch, on which there 

 were four front toes and three hind ones. Then in the Miocene were found 

 ancestors haying three toes both before and behind, while at present this 

 family is distinguished by a single functional toe on each foot, the second 

 and fourth toes forming splint bones on either side of the toe. The tibia 

 also is vestigial. 



In the Eocene times Europe and Asia were joined in the arctic latitudes 

 by way of North America. The horse inhabited all continents except 

 Australia, but it disappeared entirely from America in the later geologic 

 ages, for which no adequate explanation has been made. 2 At first it 

 was adapted to a forest life, but it has come to be more and more adapted 

 to living upon the high, dry plains, and it is one of the most highly special- 

 ized animals in its adaptation to its environment. The remains of man 

 and the horse are first found together in the interglacial or postglacial 

 period. "There is abundant proof that men first hunted and ate, then 

 drove, and finally rode the horse." 



The horse industry stands second only to the cattle industry among 

 stock men. Horsehide leather is used for razor straps, gloves, and shoe 

 uppers. The hair is used for upholstery and the bones for fertilizing, and 

 the flesh for cheap meat. The mare's milk is used by the nomadic peoples 

 of inner Asia. Koumiss, often used as a beverage, is fermented mare's 

 milk. 



All our breeds of horses have been introduced from the Old World, as 

 there have been no native wild horses in America. The ass, the zebra, and 

 the recently extinct African quagga are also members of this family. 

 The ass is wild in both Asia and Africa, and the zebra in Africa. The breed- 

 ing of the hybrid mule is confined chiefly to the southern and some of the 

 western states. 



Artiodactyla. The even-toed ungulates, in which the third 

 and fourth digits form a symmetric pair, have the three or four 

 premolars smaller than the molars, and have a complicated 

 stomach. 



The non-ruminants comprise the hippopotamus, hog, and 

 peccary. They are omnivorous. The canine teeth are fre- 

 quently developed into tusks. 



The hippppot'amus ( Hippopotam'idce) is at present confined to Africa. 

 It formerly inhabited Europe and there were also Indian species in the lower 

 Pliocene. The common hippopotamus (Fig. 271) is thick skinned and al- 

 most hairless. The two strong incisors on each side of each jaw and the 

 canine teeth continue growing throughout life. The stomach is divided 

 into two parts. The cecum is lacking. This huge animal, 14 feet long, has 

 very short limbs and tail. The feet have four-hoofed toes. The hippo- 

 potamus is nocturnal and aquatic, and not only walks rapidly along the 



1 Ingersoll, p. 378. 



2 Ibid., pp. 354-360. 



