258 
MANUAL OF MODERN FARRIERY. 
by the frog. It thus appears that by a different mechanism, 
but both equally admirable and referable to the same prin¬ 
ciple, namely, that of elasticity, the expansion of the upper 
and lower portions of the hoof are effected, the one by the 
descent of the sole, and the other by the compression and 
rising of the frog. The preservation and usefulness of the 
limbs of the horse are chiefly maintained by this upward 
expansion, when the destructive methods which are adopted 
in shoeing are calculated to destroy the expansion beneath. 
From the long-continued and violent pressure on the frog 
in draught-horses, and conveyed from the frog to the 
cartilage, inflammation is frequently produced, and too 
often terminates in the cartilages being turned into bony 
matter. 
THE FALSE CARTILAGES. 
From the inferior and posterior sides of the true car¬ 
tilages, two fibro-cartilaginous processes extend in a forward 
direction towards the heels of the coffin-bone. They spread 
inwards upon the surface of the tendo-perforans, become 
united at their inner sides with the superior margin of the 
sensitive frog, are covered inferiorly by the sensitive sole, 
and at the same time assist in the support of the sensitive 
frog. They are triangular in their form, and are arched in 
the same manner as the sole. 
Their use appears to be to fill up the triangular vacant 
spaces left between the tendo-perforans and the heels of 
the coffin-bone, thereby completing the surface of support 
for the sensitive frog, and extending that for the expansion 
of the sensitive sole. Bone in these situations must have 
proved inconvenient, by more or less impeding the impres¬ 
sion upon, and the consequent reaction of, the sensitive 
frog. 
