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, hemorrhage 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 
tar 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. Fracture 
results. 
