THE DISEASES OF THE FOOT. 403 



nisMng in teiglit forward and backward. These cartilages occupy a con- 

 siderable portion of the foot, and extend behind the cofiin-bone. They 

 are held in their sitnation not merely by this groove, but by other con- 

 nections with the coffin-bone, the navicular bone, and the flexor tendon, 

 and are thus perfectly secured. 



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

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

 which the na.vicular bone and the tendon can play with security, and 

 without concussion or shock, by which all concussion communicated to 

 the cartilages of the foot is destroyed — by which these cartilages 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 pecidiar to 

 quadi^upeds at the back of the eye, being forcibly contracted, presses 

 upon the fatty matter in which the eye is imbedded, which may be dis- 

 placed but cannot be squeezed into less compass, and which, being forced 

 towards the inner corner of the eye, drives before it that important and 

 beaiitiful mechanism the haw, so the elastic and yielding substance 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 either side of them, and expands the lateral cartilages, 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 is 

 effected, the one by the descent of the sole, the 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, inflammation is occasionally produced, which terminates iu the 

 cartilages being changed into bony matter. 



CHAPTER XIX. 



THE DISEASES OF THE FOOT. 



Of these there is a long list. 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. It will be proper to 

 commence 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 sensitive lamince, on the front and sides of the coffin-bone, being 

 I'eplete with blood-vessels, are, like every other vascular part, liable to 

 inflammation. Laminitis, or inflammation of the laminae of the feet, is 

 most prevalent amongst the heavier breeds of horses, especially when the 

 feet are flat and weak. It may be produced by several causes, but we most 

 often meet wdth it as a result of rapid and long-continued exertion on hard 

 ground. When we reflect how the feet have been battered and bruisof] 



T) n 2 



