228 THE MEANING OF EVOLUTION 
velopment which had been all pointing in one direc- 
tion has advanced very much further. The creature 
now would be undoubtedly recognized by anyone as 
a horse. The legs are longer and straighter; the mid- 
dle 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 dimin- 
ished 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 sur- 
face 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 
