Pounding along on the plateaux, which became his natural habitat, he lost one toe after another, first from his hind feet, because they do the most work in propelling him, and then from his front feet. His neck and jaw grew longer as he was obliged to reach lower and lower down to bite off the wiry grasses of the plain.
In short, the horse's foot and leg are developed from the short, slender leg and cushioned foot of, say, something resembling the foot and leg of a delicate-limbed tapir to its present form.
Compared with a man's hand, for example, the horse's knee is represented by the human wrist; the hairless spot of skin with its cushion beneath—fatty cushion of the fetlock—represents the prominence behind the root of each finger opposite the knuckles; and the hoof itself represents the nail of the middle finger of man.
PLATE III.—NEOHIPPARION
Intermediate stage in development of the horse, being about three feet high, and having three complete toes
PLATE IV.—SKULL OF HORSE EIGHT YEARS OLD