258 MANUAL OF MODERN FARPJERY. 



bj 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. 



