214 



DOMESTICATED ANIMALS AND PLANTS 



We know that several horselike forms developed in South 

 America, but that all perished for one cause or another, one at 

 least from soft teeth. It is exceedingly remarkable that while 

 the North American horse progressed almost up to the modern 



Head 



Fore Foot 



HindFoot 



Teeth 



OneToe. 



Splints of 



2nd and 4th 



digits 



OneToe 



Splints of 



2nd and 4th 



digits 



Protohippus 



Mesohippus 



Protorohippus 



ThreeToes 



Side toes 



not touching 



the ground 



ThreeToes 



Side toes 



not toiLching 



the ground 



Long- 

 Crowned, 

 Cement - 

 covered 



Three Toes 



Side toes 



touching the 



ground; 



Splint qfSthdigit 



ThreeToes 



Side toes 



touching the 



ground 



Four Toes 



Short - 

 Crowned, 

 without 

 Cement 



H3rracotherium 

 (Eohippus) 



Four_Toes 

 Splint of 

 1st digit 



ThreeToes 

 Splint of 

 5th digit 



Fig. 38. Comparative drawings of skulls, feet, and teeth of prehistoric horses, 



showing evolutionary development. Reproduced, by permission, from "Origin 



and History of the Horse," by H. F. Osborn 



type,i he became extinct for some reason, and, so far as we know, 

 before he was ever domesticated. 



What caused this extinction here and yet preserved the 

 Asiatic form till man cafne upon the earth we cannot, with our 

 present knowledge, even conjecture; though it is known that the 



1 He had reached the size of the Shetland pony with three toes, only one 

 of which rested firmly on the ground, digits II and IV being much like the 

 "dew claws" (digits II and V) of pigs ; digits I and V being represented by 

 "splints" (digits numbered I-V beginning on the inside). 



