1090 DISEASES OF THE FOOT. 



immediately acute inflammation is set up by the entrance of infective 

 substances. 



The first step in treatment is to remove the wall covering the diseased 

 spot by means of the rasp and knife without injuring the sensitive laminae ; 

 it is, therefore, necessary to note accurately the point of division between 

 the horny and vascular parts. After cleansing, as far as possible, the 

 diseased laminae, they are painted with liquor ferri perchlor ; a mass of 

 tow or jute, soaked with the same fluid, is applied, and secured by means 

 of a bandage. If proliferation from the surface of the sensitive structures 

 proves troublesome nitrate of lead may be employed ; Schleg used the 

 actual cautery. The above-described dressing should then be applied 

 and left in position for some days. When changing it, the parts are care- 

 fully examined, and if the wall has become further undermined the affected 

 horn should at once be removed, but as a rule there is no marked tendency 

 to extension. 



VIII.— CANKER OF THE SOLE AND FROG (PODODERMATITIS 

 CHRONICA VERRUCOSA VEL MIGRANS). 



Since olden times, a chronic inflammatory hypertrophic disease 

 of the keratogenous membrane of the frog and sole, sometimes 

 including the sensitive laminae, and showing a strong tendency to 

 spread to fresh areas, has been recognised and described as canker. 

 The disease consists essentially in chronic hypertrophy of the villi 

 or papillae and proliferation in the reticulum of the keratogenous 

 membrane ; the villi becoming enlarged and grouped in thin or 

 thick masses, and the cellular elements of the rete undergoing active 

 increase. Some of the villi appear atrophied, the others are irregularly 

 hypertrophied, enlarged at the base, cedematous throughout, and 

 divided at the summit into multiple secondary vesicular papillae, 

 with distended or hydropic cells. The reticular tissue is infiltrated 

 with a sero-cellular exudate, and the spaces between the groups 

 of hypertrophied villi are filled with an offensive, dark, semi-fluid 

 material. In canker, there is always partial or complete destruction 

 of the horny sole and frog, and the affected portions of the villous 

 membrane are constantly saturated with cell debris, pus, and serous 

 fluid. True horn formation is prevented, the epithelium breaking 

 down and producing a loosely attached greasy, caseous, grey layer, 

 with a characteristic, very foetid smell. As mentioned under 

 " verrucose dermatitis," canker is identical in character with so- 

 called grease, i.e., it consists in a dermatitis verrucosa ; it has also 

 been stated that either condition may produce the other, or that 

 grease may cause canker, and canker grease. Both diseases are 

 very obstinate. 



Symptoms and course. The commencement of the attack is 



