146 DISEASES OF THE HOESE'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. 



Siimx>toms. — In pumiced-foot the sole projects be3'ond the 

 level of the wall. The obliquity of the latter is more marked 

 than ill 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 w^e 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 laminae. 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, commenaes to bulge below. 



The altered character of the horn is accounted for by 

 the inflammatory changes in the sensitive laminae and the 

 papillae 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. 



