THE COFFIN-BONE. 37- 



the frog, and its elevation above the ground, are both the cause and the conse- 

 quence of contraction— the cause, as being able no longer powerfully to act in 

 expanding the heels, and the consequence, as obeying a law of nature, by which 

 that which no longer discharges its natural function is gradually removed. It 

 is, however, the cover and defence of the internal and sensible frog, which will be 

 presently treated of; enough, however, has been said to show the absurdity of 

 the common practice of unsparingly cutting it away. In order to discharge in 

 any degree, some of the offices which we have assigned to it, and fully to dis- 

 charge even one of them, it must come in occasional contact with the ground. 

 In the unshod horse it is constantly so : but the additional support given by 

 the shoes, and more especially the hard roads over which the horse is now com- 

 pelled to travel, render this complete exposure of the frog to the ground, not 

 only unnecessary, but injurious. Being of so much softer consistence than the 

 rest of the foot, it would be speedily worn away : occasional pressure, however, 

 or contact with the ground, it must have. 



The rough and detached parts should be cut off at each shoeing, and the sub- 

 stance of the frog itself, so as to bring it just above or within the level of the 

 shoe. It will then, in the descent of the sole, when the weight of the horse is 

 thrown upon it in the putting down of the foot, descend likewise, and pressing 

 upon the ground, do its duty ; while it will be defended from the wear, and 

 bruise, and injury that it would receive if it came upon the ground with the 

 first and full shock of the weight. This will be the proper guide to the smith 

 in shoeing, and to the proprietor in the direction which he gives. The 

 latter should often look to this, for it is a point of very great moment. A few 

 smiths cany the notion of frog pressure to an absurd extent, and leave the 

 frog beyond the level of the sole, — a practice which is dangerous in the horse of 

 slow draught, and destructive to the hackney or the hunter; but the majority 

 of them err in a contrary way, and, cutting off too much of the frog, lift it above 

 the ground, and destroy its principal use. It should be hit just above, or within 

 the hvelofthe shoe. 



THE COFFIN-BONE. 



The interior part of the foot must now be considered. The lower pastern, a 

 small portion of which (see d, page 345) js contained in the horny box, has been 

 already described, p. 350. — Beneath it, and altogether inclosed in the hoof, is 

 the coffin-bone, or proper bone of the foot, (see/, page 345, and d, fig. 1, page 

 350). It is fitted to, and fills the fore part of the hoof, occupying about half of 

 it. It is of a light and spongy structure (see d, fig. 1, page 350), and filled 

 with numerous minute foramina. Through these pass the blood-vessels and 

 nerves of the foot, which are necessarily numerous, considering the important 

 and various secretions there carrying on, and the circulation through the foot 

 which could not possibly be kept up if these vessels did not run through the 

 substance of the bone. Considering the manner in which this bone is inclosed 

 in the horny box, and yet the important surfaces around and below it that are 

 to be nourished with blood, the circulation which is thus carried on within the 

 very body of the bone is one of the most beautiful provisions of nature that is 

 to be found in the whole frame. No inconvenience can arise from occasional 

 or constant pressure, but the bone allows free passage to the blood, and protects 

 it from every possible obstruction. 



The fore part of the coffin-bone is not only thus perforated, but it is cmiously 

 roughened' for the attachment of the numerous minute laminae about to bo 

 described. On its upper surface it presents a concavity for the head of the 

 lower pastern, p. 350. In front, immediately above d, is a striking prominence, 

 into which is inserted the extensor tendon of the foot. At the back e, p. 345, 



