WEAR OF THE HOOF. 



193 



reaches the ground may vary in position, the toe is always the 

 last to leave it. 



If the farrier in preparing the hoof leaves one point or one 

 side of the wall too high, the portion thus left touches the 

 ground first until the inequality is removed by increased wear. 

 Were the horse under perfectly natural conditions this would 

 be of little importance, but as the shoe prevents the natural 

 remedy, and as the error is often repeated at each shoeing, any 

 injury thus produced is perpetuated. The part left too high 

 grows even more rapidly than the rest, causing the wall to 

 lose its straight direction and become curved. In the specimen 

 shown (fig. 188) the outer wall has for a considerable time been 

 left too hio;h. It will be noted 

 that the rinses lie closest together ; 

 on the low side of the hoof. If the 

 toe is left unduly long it bends 

 outwards ; if the heels are neglected 

 they are apt to bend forwards and 

 inwards. 



The hoof, moreover, wears even 

 when shod, though only at points 

 where friction can occur between it 

 and the shoe, that is, at the heels. 

 This wear is favoured by weak- 

 ness of the wall, bad quality of 

 horn, heaviness of the body, wet 

 weather, faulty shape of the hoof 

 and bearing surfaces of the shoe, and by much work on hard 

 ground. The process itself is not directly visible, but may be 

 detected by making marks on the wall and noting their dis- 

 tance above the shoe. At the next shoeing these marks will 

 be found to have approached the shoe or, in some cases, even 

 to have disappeared. Immobility of the heels, produced, for 

 example, by ossification of the lateral cartilages, diminishes or 

 entirely prevents this wear. The amount worn away between 

 one shoeing and another is certainly not much, but sufficient to 

 require attention under special circumstances. The few experi- 

 ments that have been made fix the amount thus worn away as 

 from to -J- inch per month. The inner heel usually wears 

 more quickly than the outer. The form of the friction surface 



N 



Fig. ISS.— Overgrown and laterally 

 distorted hoof. 



