MAMMALS. 



117 



there being but one (the middle or third) in each foot. In 

 the skeleton, however, traces of two more can 

 be found in the "splint-bones," two small 

 bones occurring alongside the large "cannon- 

 bone." All of the existing horse-like forms 

 have the teeth i }, c |, p -, m f , and all are 

 natives of the Old World, none existing in 

 America at the time of its discovery. All 

 evidence goes to show that the home of the 

 domestic horse was in Central Asia, and indeed 

 four different species of horse run wild there 

 to-day. The asses have their centre around 

 the eastern end of the Mediterranean, while 

 the zebras or striped horses are all African. In 

 geological time, however, America had horses, 

 and the fossils in our Western States give the Fro . 4g._Foot 

 history of the race from small forms about the showing the 

 size of a fox, and with three toes behind and 

 four in front; later, those as large as a sheep, 

 with three functional toes in each foot; and 

 still later, three-toed forms as large as a donkey. In 

 domestication horses vary extremely in size as in other 

 respects. 



Lowest of the artiodactyls, or even-toed ungulates, come 

 the two species of hippopotamus, in which there are four 

 toes, large canine teeth, and a huge, clumsy body, some- 

 times fourteen feet in length. In the pigs the canines are 

 still large, and the toes are four in number, but the outer 

 ones are lifted above the ground so that they are useless as 

 organs of locomotion. Our domestic swine have descended 

 from the wild-boars of Europe. In the warmer parts of 

 America the peccaries represent the group. 



The hippopotamus and the pigs have the axis of the 





