184 THE STRUCTURE OF THE HORSE. 



been made, none of which will bear examination. 

 One of the most plausible, especially in the light of 

 modern comparative anatomy, is that they are rudi- 

 ments or vestiges of the inner toe the thumb or 

 pollex of the fore limb, the great toe or hallux of the 

 hind limb which, as already shown, is not otherwise 

 represented in the horse. There are, however, many 

 objections to this theory. The inner toe is always 

 the first to disappear in all mammals, and no traces 

 of it are found in any ungulate, either Perissodactyle 

 or Artiodactyle, except the most ancient forms. It 

 is, therefore, most unlikely that anything of this 

 digit should remain in the horse after the complete 

 disappearance of the second, fourth, and fifth. In 

 the next place, there is nothing beneath the modified 

 patch of skin showing any trace of the structure of 

 a toe, and the resemblance of this patch to a hoof is 

 of the very slightest character, and, indeed, in the 

 donkeys and zebras none whatever. But the most 

 serious objection is the situation of the one that is 

 most constant that on the fore limb where it is 

 placed, not on the hand, as it would be if it repre- 

 sented the thumb, but upon the forearm, at some dis- 

 tance above the wrist- joint. Lastly, such a hypoth- 

 esis is quite unnecessary, for they obviously belong 

 to a numerous class of special modifications of par- 

 ticular parts of the cutaneous surface which occur in 



