162 DISEASES OF THE HORSE'S FOOT 



Complicated when deep enough to allow of laceration and 

 subsequent inflammation of the keratogenous membrane. 

 Such complications may vary from a simple inflammation 

 set up by laceration and irritation of the sensitive structures 

 by particles of dirt and grit that have gained entrance 

 through the crack, to other and more serious changes in the 

 shape of the formation of pus, haemorrhage from the 

 laminal vessels, caries of the os pedis, or the development 

 of a tumour-like growth of horn on the inner surface of the 

 wall known as a keraphyllocele. 



(d) Their Duration. — Recent when newly formed; old 

 when of long standing. 



(e) Their Starting-point. — This last distinction we make 

 ourselves, and, referring to cracks of the wall, term them 

 high when commencing from the coronary margin, low 

 when starting from the bearing surface. 



Causes. — We have already classified sand-crack as a 

 disease arising from faulty conformation. Thus, in just so 

 far as a predisposing build of body may be handed down 

 from parent to offspring, we may regard sand-crack as 

 hereditary- If we do so, however, we must afterwards 

 make up our minds to sharply distinguish between the sand- 

 crack plainly brought about by accidental cause, and that 

 occurring as a result of hereditary evil conformation. 



With regard to the latter, we need hardly say that feet 

 with abnormally brittle horn are extremely liable. But 

 with this, as with many other affections of the feet, we 

 shall find it necessary to consider several causes acting in 

 cooperation. In this case, for instance, given the brittle 

 horn, it becomes necessary to further look for exciting 

 causes of its fracture. 



We will take conformation first. In the animal with 

 turned-out toes a more than fair share of the body-weight 

 is imposed on the horn of the inner quarter. Here, then, 

 three causes exert their influence together : The horn is 

 brittle; the wall of the inner quarter is thinner than that 

 of the outer; additional weight is imposed upon it. Frac- 

 ture results. 



