276 HOOFED ANIMALS 



Looking at the legs of a Horse, the question arises what 

 has become of all the toes. In the animals which divide 

 the hoof there are apparently only two toes to each foot ; 

 but a very superficial examination shows us that two other 

 toes are only partly developed, and are absolutely useless as 

 a means of progression. But examine the foot of the Horse, 

 and to all appearance there is but a single toe, until we strip 

 off the skin as far as the knee of the fore limb and the hock 

 of the hind leg. 



The normal number of digits (i.e., fingers and toes) is 

 five ; but we have seen how various bones are often 

 extremely modified. The thumb of the fore feet, or the 

 great toe of the hind feet, is invariably the first in which 

 development is arrested, and the others are modified 

 according to the needs of the possessor. What, then, is 

 this single toe of the Horse ? We must transport ourselves 

 to the Eocene epoch to find the animal termed the 

 Eohippus, i.e., the Dawn of the Horse. It was little 

 more than the size of a fox terrier, with four complete 

 toes on the fore feet, and the rudiments of a thumb dis- 

 tinctly marked ; on the hind feet were three toes. In the 

 Miocene period the thumb disappears altogether and the 

 digits are still more reduced, until in the Pliocene, 

 the creature had greatly increased in size, and the digits, 

 with the exception of the third and fourth (counting the 

 thumb as the first), were fused together so as to look as if 

 they were a single bone. 



It is now comparatively easy to understand the con- 

 struction of the foot of the Horse, as shown in the illustra- 

 tion. The left-hand figure represents the fore-foot, or, as it 

 might be called, the hand. Beginning at the top, we see 

 the end of the radius, and below it the carpal bones, i.e., 

 those of the wrist. One projects beyond the others, and 

 this is the rudimentary thumb. Below the carpal bones is 

 a stout and straight bone, called the cannon bone. It is 

 not a single bone, but is composed of the third and fourth 

 metacarpals, which are fused together. At the side of the 

 cannon bone may be seen a slight, elongated bone, with 

 another of the same dimensions on the opposite side. 

 These are the second and fifth metacarpals (i.e., the first and 



