464 CHAPTER G2. 



horn libres having' bt'cii destroyed, tlie nails have a loss liini hold and 

 consequently the shoe is more easily i)ulled ofi", and probably a consider- 

 able jiortion of the weakened crust will come away with it. 



945. Why then do farriers rasj) the Crust / 



First, because an aj)i)arently good tit of the shoe to the foot is essen- 

 tial. Secondly, because it is easier to produce to the eye of an inexiteri- 

 enced person the appetvrance of u good tit by rasping down the foot to a 

 shoe rather too small for it than to tit the iron to the real size and shape 

 of the foot. 



The i)rim(tnj esiciitial of all yood shoiiny is tliat the untm/c of (he 

 CI Hit he not rasped. 



1*4:0. Of lowering the crust versus raajiing its exterior surface. 



The crust or wall having been protected by the shoe from that natural 

 friction and wear against the ground to which it would have been sub- 

 jected if it had not been so protected, it is necessary each month to lower 

 the crust as niuch as will rej^resent what would have been the natural 

 detrition by wear. 



Hov, much this will be nmst vary in different horses. In some feet 

 the growth is much more rapid than in others. In some hoofs of soft 

 material the crust wears away considerably, even though protected by a 

 shoe. This question must be left to the practical and practised eye of 

 the farrier. 



But it will be asked, How is the crust to be lowered without causing 

 the injuries described above to its structure I 



Simply by removing all that requires to be removed from the inferior 

 or ground surface of the crust, without touching the superior part. This 

 will be best done by the rasp from underneath, though, if the crust be 

 vei\y long, the knife may be used (a, tig. 4). 



After a sufficient quantity has been removed, the inferior or ground 

 surface nmst be made perfectly level, for the reception of the shoe, by 

 the use of the rasp. 



The strength of the fibres of the crust will not be in any degree less- 

 ened by shortening them. On the contrary, it will be rather increased. 

 Let me illustrate what I mean by an ordinary (juill or pencil. If I shave 

 it longitudinally it will be weakened as regards its i)ower of sustaining 

 weijrht on its top ; but if I cut half an inch or an inch off its lower end 

 it will practically be strengthened. For illustration see A, figs. 2 and b, 

 as compared with a, fig. 4. 



947. Prevention of Sjditting of the Crust after leing lowered. Feather 



edge. 



When the crust has been sufficiently lowered and made level by the 

 rasp, as above described, it will be sharp all round its exterior circle. 

 This sharp or feather edge must be removed by the rasp before the shoe 



