INFLAMMATION OF THE FOOT. 289 



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

 and on either side of the frog. 



Between these cartilag-es 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 without concussion or shock — by which all concussion 

 communicated to the cartilages of the foot is destroyed — and 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 peculiar to quadrupeds at the back of the eye (see page 88), being 

 forcibly contracted, 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 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 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, 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, 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 fleshy plates on the front and sides of the coffin- 

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

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

 violence with which, in rapid and .long-continued action, they are lengthened 

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

 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 battered and 



