AND HOW TO KEEP IT SOUND. 11 



tlons of the bone, is induced ; for it is an invariable law of 

 the animal economy not to continue to unemployed structures 

 the same measure of efficient reparation that is extended to 

 parts constantly engaged in performing their allotted tasks. 

 The shoe restricts or prevents expansion ; while Nature, as 

 the secret influence is called, immediately sets to work to 

 simplify the apparatus for producing the expansion, which 

 art has thus rendered impracticable, and substitutes f jr it a 

 new structure, less finely organized, but admirably suited to 

 the altered condition of the parts. 



The wings extend from the body of the bone directly back- 

 wards, and support the "lateral cartilages" of the foot. 



If a coffin bone be placed upon a flat surface, it will be 

 seen that the whole of the front of the toe is considerably 

 raised or arched, as if a notch had been cut out of it, giving 

 it almost the appearance of an imperfect bone.* I consider 

 this to be one of the numerous provisions of nature for dimin- 

 ishing the concussion to which the horse's foot is so constantly 

 exposed ; for if the toe of the bone corresponded exactly with 

 the toe of the hoof, a shock would be communicated to the 

 whole foot each time it struck against a stone or other pre- 

 lecting substance ; whereas this intervening space, by break- 

 ing the connection of the parts, almost entirely prevents the 

 transmission of the jar. This conjecture is greatly strength- 

 ened by the fact, that the coffin bone of the hind foot, where 

 the jar would be less felt, presents no such deficiency at the 

 toe. 



The coronet bone is nearly square ;f its breadth from side 

 to side exceeds its height by about one-fifth ; it is situated 

 partly within, and partly without the hoof;:]: it supports the 

 pastern bone, and rests upon the coffin and navicular bones. 



The lateral cartilages are attached to the upper edge of 

 the wings of the coffin bone, and project backwards beyond 

 the bone, giving form and substance to the heel. About half 

 of each rises above the hoof as high as the pastern joint, and 

 can be distinctly felt under the skin. 



The sensitive covering to the coffin bone is a prolongation 

 of the coronary substance : it is firmly attached to the surface 

 of the bone, and is collected into numerous little plaits or folds, 

 which run in parallel slanting lines down its sides. 



The sensitive sole, or, as it is sometimes called, the fleshy 

 sole, is about the eighth of an inch thick, and is almost entire- 



• Page 49, %. 4 t Page 40, fig. 3. t Page 50, fig. G. 



