146 DISEASES OF THE HORSE’S FOOT 
D. PUMICED-FOOT, DROPPED SOLE, OR CONVEX SOLE. 
Definition.—This term is applied to the foot when the 
shape of the sole is comparable to the bottom of a saucer. 
When least marked it is really an aggravated form of 
flat-foot. 
Symptoms.—In pumiced-foot the sole projects beyond the 
level of the wall. The obliquity of the latter is more marked 
than in the previous condition, and progression, to a large 
extent, takes place upon the heels. In addition to its 
deformity, the horn is greatly altered in quality, and, as 
the name ‘ pumice’ indicates, is more or less porous in 
appearance, bulging, and brittle. 
Causes. —As a general rule, it may be taken that pumiced- 
foot is a sequel of previous disease, although in its least 
pronounced form it may occur as the result of accidental 
or other causes, such as those described in the causation 
of flat-foot. 
Occurring in its most marked form, there is no gain- 
saying the fact that pumiced-foot is a sequel of either acute 
or subacute laminitis. As we shall see when we come to 
study that disease, the dropping of the sole is brought 
about by distinct and easily-understood morbid processes 
affecting the sensitive structures. Briefly, these morbid 
processes in laminitis may be described thus: The accumu- 
lated inflammatory exudate, and in some cases pus, weakens 
and destroys the union between the sensitive and insen- 
sitive lamine. This separation, for reasons afterwards to 
be explained, is greatest in the region of the toe. The 
os pedis, loosened from its intimate attachment with the 
horny box, is dropped upon the sole, and the sole, unable 
to bear the weight, commences to bulge below. 
The altered character of the horn is accounted for by 
the inflammatory changes in the sensitive lamine and the 
papille of the keratogenous membrane generally, for it 
follows as a matter of course that these tissues, themselves 
in a diseased condition, must naturally produce a horn of 
a greatly altered and inferior quality. 
