In the Stable, Field, and on the Road. 83 



each side, except at the protuberance which receives the 

 extensor tendon, and which extends to the very posterior 

 portion of the foot, rising at the quarters fully half-an- 

 inch above the hoof, and diminishing in height backward 

 and forward. These cartilages occupy a greater portion of 

 the foot than the coffin-bone, which they extend far behind, 

 and are fixed into two grooves excavated into the superior 

 lateral borders of the coffin-bone, the navicular bone, and 

 the flexor tendon, and are thus perfectly secured. Below 

 these are other cartilages connected with the under edges 

 of the former, and on both sides of the frog. Between 

 these cartilages is the sensitive frog, occupying the whole 

 of the space, and answering several important purposes, 

 it being an elastic bed upon which the navicular bone 

 and the tendon can play with security, and without con- 

 cussion to the cartilages. By this means all concussion 

 to the cartilages of the foot are prevented, the cartilages 

 kept asunder, and the expansion of the upper part of the 

 foot preserved. This mechanism is both beautiful and 

 important. The yielding and elastic substance of the 

 frog is pressed upon by the navicular bone, as well as by 

 the tendon and the pattern, and being incapable of con- 

 densing itself into less compass is forced out on each side 

 of them and expands the lateral cartilages. These again 

 by their inherent elasticity revert to their former situa- 

 tion when they are no longer pressed outward by the frog. 

 It thus appears that by a different mechanism, but 

 both equally admirable and referable to the same 

 principle of elasticity, the expansion of the upper and 

 lower parts of the hoof are affected ; the one by the 

 descent of the sole and the other by the compression and 



