her. The
creature now would be undoubtedly recognized by anyone as a horse. The
legs are longer and straighter; the middle toe has become the only
useful toe, though on each foot a smaller toe, slender and probably
useless, still hangs on either side. Two similar useless toes to-day
hang at the back of the foot of the cow, which is now walking upon her
two toes, which give her the appearance of carrying a cloven hoof.
That is to say, the first toe on the foot of the cow has disappeared,
the second and fifth hang useless and much diminished at the back of
the foot, while the third and fourth are both well developed and
serviceable in walking.

The late Tertiary horse has grown to be the size of a burro of to-day,
though probably it was a little more slender. The teeth are quite
horselike, both in shape of the crescentic ridges on their surface, in
the length of the teeth in the jaw bone, and in the fact that the
crinkled edges of enamel on the upper surface are protected on either
side by dentine or by cement. These surfaces, being softer than the
enamel, wore away somewhat more rapidly and allowed the sharp edges of
enamel to stand up in ridges. This plan increases the grinding power
of the teeth.

With the oncoming of the Era of Man the horse reaches his modern
splendid development. During the early Quaternary the horse was
perhaps in some of his representatives a larger creature than he is
to-day. Each foot now has but a single toe. The nail has spread around
firmly and heavily, until it has become a splendidly developed hoof,
permitting the animal to travel with speed over firm and often stony
ground. The side toes have disappeared completely from the outside of
the horse's leg, although upon removing the skin it is easy to find
the long splints, which are the remnants of toes, which have not yet
quite disappeared. His heel has been lifted in the air until it is
eighteen inches off the ground, and he is standing like an expert
dancer upon the tip of his toe. The body of the horse thus being
lifted far off the ground, a new development becomes necessary. All
through the growth of the creature the neck and head have been obliged
to lengthen correspondingly. Every animal must be able to bring its
head down to the level of its feet in order that it may drink. Various
animals use different methods to accomplish this result. The giraffe,
with his enormously long legs, has a correspondingly long neck, which
lowers his mo