598 OPERATIONS ON THE FOOT. 



and even with Vatel and Hurtrel d' Arboval, who looks upon canker 

 as the carcinoma of the reticular structure of the foot. 



It is but recently that these ideas have been abandoned. Du- 

 puy, in 1827, considered canker as a hy^Dertrophy of the fibres of 

 the hoof, admitting at the same time the disintegrations and 

 softening of those same fibres occasioned by an ammoniacal sap- 

 onization produced by an altered secretion. 



In 1841, Mercier expressed the opinion that canker is nothing 

 more than a chronic inflammation of the reticular tissue of the 

 foot, characterized by diseased secretions of this apparatus. 



It is now known that there is in canker no essential alterations 

 of the sub-horny tissues ; no radical change of their substance, 

 and no deposit of heteromorphous molecules in theu* structure. 

 This last mentioned fact was well observed by Kobin, who in his 

 microscopical remarks constantly observed the absence of the 

 characterizing elements of canker. Hertwig and Haubner, who 

 have made researches in the same direction, arrived at the same 

 result and have noticed the absence of any cancerous cells in 

 canker. This opinion is, however, doubted by GHsberg and Fuchs, 

 who look ujDon canker as an epithelioma, though they bring no 

 sufl&cient evidence to establish it. 



Except vegetal parasitism, of which we will speak hereafter, 

 and which makes of canker a true dartre, an herpetic disease, as 

 demonstrated by Megnin, there is only in canker a chronic in- 

 flammatory condition of the sub-horny tissues which is mani- 

 fested by a perversion in their secretion, and is complicated by 

 a morbid hyj^ertroj^hy of the villous processes by which their sur- 

 face is normally covered. Eobin has seen in the fici, papillae made 

 thicker and more brittle by the plastic infiltration which moistens 

 them; he has observed besides, that at the points where the secre- 

 tion is good, it is so active, that instead of drjdng in sheaths, to 

 scale off afterward in transverse pieces, as normally occurs in the 

 frog and sole, the epithelial cells grow lengthwise, as those which 

 form the walls of the foot. Hence these long, horned, twisted 

 threads (epithelioma?) which are seen rising from the sole of long 

 affected cankerous feet. 



It has sometimes been admitted that fici had deep roots in the 

 tissues, and even in the plantar aponeurosis, which is an eiTor ; 

 injections and macerations ha\ang shown that there are no essen- 

 tial changes in the anatomical structiu'es of these parts, and that 



