136 HORSES AND ROADS. 



the description which Mr. Douglas gives of the 

 constituency of the crust. He is well worth hearing 

 twice : 



6 If the crust is closely examined with a micro- 

 scope, its structure will be found to consist of a 

 number of bristle-like fibres standing on end, but 

 bearing diagonally towards the ground. From the 

 particular longitudinal construction of the fibres, it 

 follows that they will bear a great amount of weight, 

 so long as they are kept in their natural state. The 

 crust so viewed resembles a number of small tubes, 

 bound together by a hardened glue-like substance. 

 Whoever has seen a mitrailleuse gun, with its 

 numerous barrels all soldered together, can form a 

 very good idea of the crust, especially if they were 

 likewise to imagine the tubes to be filled with a 

 thick fluid the use of which is to nourish and 

 preserve them.' 



We have already seen that the driving of nails, 

 in any form, must both lacerate and close up, either 

 totally or partially, these delicate tubular fibres con- 

 taining the fluid which gives life ; but when we 

 come to consider that in driving them askant from 

 right to left the farrier is causing a double amount 

 of laceration, we shall easily comprehend that the 

 further the disease spreads, the more he helps it 

 to do so. Well may Mr. Lupton say : ' Farriers 

 ought to go through a course of instruction pre- 

 viously to being allowed to operate upon structures 

 the anatomy, physiology, and economic uses of which 

 they have never studied, and, consequently, never 

 understood.' 



