INFLAMMATION OF THE FOOT. 289 



Below are other cartilages connected with the under edges of the former, 

 and on either side of' tiie frog. 



Between these cartilages is the sensible frog, filling up the whole of the 

 space, and answering several important purposes, being an elastic bed on 

 which the navicular-bone, and the tendon (see page 249), can play with 

 security, and with concussion or shock, by which all concussion communi- 

 cated to the cartilages of the foot is destroyed, and by which these carti- 

 lages are kept asunder, and the expansion of the upper part of the foot 

 preserved. As the descent of the sole increases the width of the lower 

 part of the foot, so the elevation of the frog, a portion of it being pressed 

 upward and outward by the action of the navicular-bone and tendon, causes 

 the expansion of its upper part. Precisely as the strong muscle peculiar 

 to quadrupeds at the back of the eye (see page 88) being forcibly con- 

 tracted, presses upon the fatty matter in which the eye is imbedded, which 

 may be displaced, but cannot be squeezed into less compass, and which, 

 being forced towards the inner corner of the eye, drives before it that 

 important and beautiful mechanism of the haw, so the elastic and yielding 

 substance of the frog, being pressed upon by the navicular-bone and the 

 tendon, and the pastern, and refusing to be condensed into less compass, 

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

 and which again, by their inherent elasticity, recur to their former situation, 

 when the frog no longer presses them outward. It appears, that by a 

 different mechanism, but both equally admirable, and referable to the same 

 principle, viz., that of elasticity, the expansion of the upper and lower 

 portions of the hoof are effected, the one by the descent of the sole, thn 

 other by the compression and rising of the frog. 



It is this expansion upward, which contributes principally to the preser- 

 vation of the usefulness of the horse, when our destructive methods of 

 shoeing are so calculated to destroy the expansion beneath. In draught- 

 horses, from the long continued, as well as violent pressure on the frog, and 

 from the frog on the cartilage, inflammation is occasionally produced, which 

 terminates in the cartilages being changed into bony matter. 



CHAPTER XVI. 



THE DISEASES OF THE FOOT. 



Of these, we have a long list to lay before our readers, but that will not 

 be wondered at by those who have duly considered the complicated structure 

 of the foot, the duty it has to perform, and the injuries to which it is exposed. 

 We begin with that which is the cause of many other diseases of the foot, 

 and connected with almost all. 



INFLAMMATION OF THE FOOT, OR ACUTE FOUNDER. 



The sensible lamellae, or the fleshy plates on the front and sides of the 

 coffin-bone, being replete with blood-vessels, are, like every other vascular 

 Dart, liable to inflammation, from its usual causes, and particularly from 

 the violence with which, in rapid and long-continued action, they are length- 

 ened and strained. When in a severely contested race they have been 

 stretclied to the utmost ; while, at the fullest stride of the horse, his weight 

 was thrown on them with destructive force; or, when the feet have been 

 \)atterea and bruised in a hard day's journey, no one will wonder if inflam- 



