THE SOLE. 285 



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 gradu- 

 ally removed. It is, however, the cover and defence of the internal and 

 sensible frog, 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 show 

 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 

 ^f the shoe. It will then, in the descent of the sole, when the weight of 

 che horse is thrown upon it in the putting down of the foot, descend like- 

 wise, and pressing upon the ground, do its duty ; while it will be defended 

 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 o^ frog pres- 

 sure 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 wUJiin the level of 

 the shoe. 



THE SOLE. 



This is the under concave and elastic surface of the foot (see h, p. 283), 

 extending 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 f is driven forward and downward in that direction. It is like- 

 wise 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 prin- 

 cipally 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 

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



