CAUSES OF UNSOUNDNESS. 103 



answer can be given. It is a degenerative process 

 — a deposition of lime-salts in the cartilage — and 

 most degenerative processes are slowly developed, 

 so that it is, in all probability, the work of 

 months, and with advancing years, there is a 

 natural tendency for this change to occur. 



Sand-crack. 



This disease is indicated by a small crack or 

 fissure in the hoof, and may be situated on either 

 the fore, or hind foot. If in the former, it is usually 

 at the inner quarter of the hoof, the horn being 

 thinnest there. It is generally at the toe, in the hind 

 feet. A sand-crack may be superficial or deep, 

 but in every case is regarded as constituting un- 

 soundness. If it is superficial the outer layer of 

 horny tubes composing the wall only are affected, 

 but when deep, the whole thickness of the wall is 

 impHcated, so that severe lameness may result 

 through the fissure in the wall nipping the sensitive 

 structures on the face of the pedal bone. Sand- 

 crack usually begins at the top of the hoof, and 

 what may, at first, apparently be but a most trifling 

 matter, not uncommonly turns out to be a trouble- 

 some disease of the foot. Bearing this in mind, 

 the upper border of the hoof should always be 



