THE SOLE. 285 



Seduence of contraction : the cause, as being able no long'er 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 

 fro"-, at which we are not yet arrived, and therefore we are at present 

 unable to develop its full use ; but we have said enough to shew the 

 absurdity of the common practice of unsparingly cutting it away. To 

 discharge, in any degree, some of the offices which we have assigned to 

 it, and "fully to discharge 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 compelled 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 substance 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 de- 

 fended from the wear, and bruise, and injury which 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 operating, and to the proprietor 

 in the directions which he gives ; and the latter should often look to this, 

 for it is a point of very great moment. A few smiths carry 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 left just above, or 

 within the level of the shoe. 



THE SOLE. 



This is the under concave and elastic surface of the foot (see 6, p. 283), ex:- 

 tending from the crust to the bars and frog. It is not so thick as the crust, 

 because, notwithstanding its situation, it has not so much weight or 

 stress thrown on it as there is on the crust ; and because it was intended 

 to expand, in order to prevent concussion, when, by the descent of the 

 bone of the foot, the weight was thrown upon it. It is not so brittle as the 

 crust, and it is more elastic than it. It is thickest at the toe (see t, page 

 249), because the first and principal stress is thrown on that part. The 

 coffin bone/ is driven forward and downward in that direction. It is 

 likewise thicker where it unites with the crust than it is towards the centre, 

 for a similar and evident reason, because there the weight is first and 

 principally thrown. 



In a state of nature it is, to a certain degree, hollow. The reason of 

 this is plain. It is intended to descend or yield with the weight of the 

 horse, and by that gradual descent or yielding most materially lessen the 

 shock which would result from the sudden action of the weight of the 

 animal in rapid and violent action ; and this descent can only be given by 

 a hollow sole. A flat sole, already pressing upon the ground, could not 

 be brought lower ; nor could the functions of the frog be then discharged ; 



