298 



THE FORE LIMB. 



The Hoof corresponds to the nail of our third finger 

 or toe, or to the claw of the third toe of the dog. The 

 frog is a horny accessory structure to the hoof, and is 

 placed immediately behind the sole. As pointed out to 

 me by Professor Ewart, the sole corresponds to the palmar 

 surface of the third phalanx of the middle finger of man ; 

 and the frog, to the palmar surface of the second phalanx. 



Photo by] [M. H. H. 



Fig. 376. — Horizontal section through donkey's near hind hoof. 



This is well shown by the fact that the horse's frog is 

 formed out of a pad which, in the eight weeks' embryo, 

 lies under the short pastern bone (2nd .phalanx). In the 

 horse, it is so closely connected with the hoof, that it is 

 usually regarded as a portion of the hoof. This connection 

 is not so close in the donkey, as we may see in Fig. 376. 

 In the horse, it acts as a buffer (pad), to diminish the 

 bad effects of concussion during movement. 



