104 HORSE AND MAN. 



injure the hoof is the three-clamped ring which has 

 already been mentioned. Nails, however few or slight, 

 however well they may be made, or how skilfully 

 they may be driven, must injure the wall, even if it 

 be perfectly sound and hitherto untouched. 



If the hoof were a mere solid, self-renewing block 

 of horn, without any particular structure, no very 

 great harm would ensue, as the nails would only 

 make holes which would be soon filled up again. 

 But the only part of the hoof into which a nail 

 can be driven is the wall, which is made, as has 

 been said before, of flat fibres laid side by side. 



Now, all shoenails are made on the principle 

 of the wedge, and if a wedge be driven between 

 parallel fibres, it must tear them apart. The rent 

 thus made is of course most conspicuous at the 

 nail-hole, but is necessarily continued above arid 

 below it. 



On an average, eight nails are used in a shoe, 

 and on an average each nail is at least one- eighth of 

 an inch in thickness. So, by inserting these nails, 

 the farrier is driving a full inch of iron among the 

 fibres of the wall, tearing them apart at the nail-holes, 

 and crushing them together at each side, thus de- 

 stroying the whole character of the horn. Then, 

 after the shoes have been removed and replaced a 

 few times, the horn becomes so weakened that it will 



