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 



