THE EVOLUTION OF THE HORSE
general pattern to the common mammalian foot, but the stress for speed appears to have centered on the third toe, leading to the elimination of four of the toes, resulting in a one-toed, swift-running animal, as the geological record shows. Relics of two of the last toes to disappear are seen in the splint bones of the modern horse.
The geological record reveals to us, of course, only the bony parts of the numerous horses whose remains have been preserved in the rocks and discovered. The differences in these parts have enabled us to discriminate many species, but if we knew the differences in mane and in tail and in colour we might increase greatly the number of species. We do know enough to assure us that a continuous series of horse-like forms inhabited the earth for ages and that Western North America was the principal scene of their remarkable development. All the American horses, however, finally became extinct from some cause or causes not yet discovered, perhaps a parasitic or a contagious disease. Thus the horse, which lived and developed for more than forty million years in America, died out on its native soil; but it survived in the Old World, though in smaller numbers and in forms less varied than it had in America in the Ice Age.
When America was discovered and explored by Europeans there were no horses in the country. Although some horses escaped from the Spanish. conquerors and became wild, both in North America and South America, our domestic horse is a descendant of European breeds, which are numerous and extremely diverse in size as well as in other features.
In early historical time the domesticated horse was used to draw chariots and as a riding animal. From the earliest stages of its domestication it was highly prized. The horses of one country were traded for those of another, or were captured, and great care was taken in their breeding. Some of
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