THE LIMBS. 181 



position of the horse's foot, standing only on the end 

 of the last joint of the one toe, this part of the foot 

 no longer comes to the ground, and yet the pad with 

 its bare and thickened epidermic covering, greatly 

 shrunken in dimensions and concealed among the 

 long hair around, and now apparently useless in the 

 economy of the animal, remains as an eloquent testi- 

 mony to the unity of the horse's structure with that 

 of other mammals, and its probable descent from a 

 more generalized form, 'for the well-being of whose 

 life this structure was necessary. 



The ergot of the horse, placed in the middle line 

 of the foot, must not be confounded, as has some- 

 times been done, with the parts bearing in French 

 works the same name in the ox, and which are placed 

 one on each side in a somewhat similar part of the 

 foot. These are clearly shown by the structure of 

 their horny covering, by the presence of bony ele- 

 ments within, and by comparison with their more 

 developed condition in other ruminants, to be really 

 the hoofs of the second and fifth digits, reduced to 

 a very rudimentary condition. 



Besides the ergot there are other patches, more 

 obvious to ordinary observation, in which the skin is 

 peculiarly modified from its usual structure. These 

 are the so-called " chestnuts," or " mallenders " and 

 '< sallenders " as they are designated in old books. 



