OUTLINE OF THE STEUCTUEE OF THE HOESE. 41 



longest in front, where its extreme point is called the toe. 

 Behind it is open, and the crust terminates in a thick," por- 

 ous skin, divided by a seam at the back part of the foot, 

 and presenting two convex, lateral extensions, which together 

 are called the heel. At the top of the crust, where it unites 

 with the hair, is the coronary ring. This is a thick, spongy 

 substance — soft hoof, in fact, in process of formation. It is 

 to the horse's feet what the roots of the nails are to the 

 human fingers and toes. Another crust, less brittle, and 

 more elastic, extends under the foot, forming the sole, and 

 presenting a somewhat concave surface to the ground. At 

 the back part of the foot is a horny projection in the shape of 

 a letter Y, with its opening toward the heel. The two sides 

 of this projection, which should unite at an angle of about 

 forty-five degrees, are called the bars. What horsemen call 

 the inside quarter of the foot, is that part without the bars, 

 next to the opposite foot. The outside quarter lies upon the 

 other side of the foot. Within the bars is the frog. This 

 is of the color of dark India-rubber, which substance it re- 

 sembles in its degree of toughness and hardness, but possesses 

 less elasticity. The entire crust of the frog is insensible, but 

 at the depth of about half an inch is found the sensible or 

 living portion, exceedingly tender, and filled with innumer- 

 able little nerves and blood-vessels. 



Inside of the hoof are two spongy bones — the coffin and 

 shuttle-bones {os pedis and os naviculare) — which are, at times, 

 the seat of most obstinate disease. These occupy little more 

 than one-half the space within the hoof; the remainder is 

 filled by cartilages, tendons, and muscles, through which 

 ramify a greater proportionate distribution of little nerves 

 and blood-vessels than can be found in any other part of 

 the body. 



There is a very important tendon (the flexor tendon), ex- 

 tending from the back part of the lower pastern bone {ps 

 coronce) and coffin-joint over the extremity of the shuttle- 

 bone, where it divides into two parts, which pass down 

 upon each side of Jhe indentation of the heel and frog, and 



