THE CARTILAGES OF THE FOOT. 257 



THE CARTILAGES OF THE FOOT. 



The cartiLages are two broad, scabrous, concavo-convex 

 cartilaginous plates which surmount the sides and wings of 

 the coffin-bone. There is a groove extending along the 

 upper part of the coffin-bone on each side, except at the 

 protuberance, which receives the extensor tendon, and which 

 extends to the very posterior portion of the foot, rising 

 about the quarters fullj half-an-inch above the hoof, and 

 diminishing in height backward and forward. These car- 

 tilages occupy a greater portion of the foot than does the 

 coffin-bone, as will be observed in lig. 7, plate vii., i, where 

 it Avill be seen thej extend far behind the coffin-bone. 

 They are fixed into two grooves, excavated in 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 fros;. 



Between these cartilages is the sensible frog, occupying 

 the whole of the space, and answering several important 

 purposes, it being an elastic bed on which the navicular bone 

 and the tendon can play with security, and without con 

 cussion. This will be understood by referring to plate vi, 

 fig. 10, /. Thus all concussion to the cartilages of the foot 

 is prevented, and these cartilages kept asunder, and the 

 expansion of the upper part of the foot preserved. This 

 mechanism is both beautiful and important. Tlie yielding 

 and elastic substance of the frog is pressed upon by the 

 navicular-bone as well as the tendon and the pastern, and 

 being incapable of condensing into less compass, is forced 

 out on each side of them, and expands the lateral cartilages ; 

 and these again, by theit inherent elasticity, revert to their 

 former situation, when they are no longer pressed outward 



2 L 



. ♦ 



