THE LIMBS 



189 



under surface of the horse's foot with the tip of the human 

 finger, the free or lower edge of the wall of the former 

 corresponds with the free edge of the nail of the latter, 

 only vastly more developed in extent, in complexity of in- 

 volution, and in thickness; the frog and all its accessory 

 parts to the rounded free tip and bulb of the finger 

 also greatly developed, so as to form the heel-like pro- 

 jection so essential to give stability to the horse's foot in 

 standing ; while the sole is only represented by the thin 

 curved line between the under surface of the nail and the 

 skin covering the tip of the finger. 



Comparing the horse's toe with that of a clawed 

 animal — a dog or cat, for instance — the wall of the hoof 

 represents the horny sides of the claw ; the sole the 

 narrow soft under surface of the claw, where the edges 

 do not meet ; the frog and its branches and glomes the 

 smaller, oval bare pad under the toe ; while the ergot or 

 bare space behind the fetlock-joint represents (as shown 

 before) the large pad under the middle of the foot. 



The hoofs of asses and zebras, though formed on 

 exactly the same general plan as those of the horse, 

 differ in being smaller and especially narrower. The 

 different parts of the inferior surface, the wall and bars, 

 the sole and the frog, can be made out, though they are 

 less distinctly marked from each other than in the horse. 



The mechanical arrangement of the under surface 

 of the horse's hoof in its natural state is admirably 



