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 fully 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 fig. 7, plate vii., i, where 
it will be seen they 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 frog. 
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, 1. 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. The 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 their inherent elasticity, revert to their 
former situation, when they are no longer pressed outward 
