134 
A. ZUNDEL 
which seem to form a homogeneous mass, constitute, however, an 
aggregate of smaller vegetations united in a certain part of their 
extent, and continued at their bases. 
Besides the vegetation of the living tissues, the plantar surface 
of the foot presents, in old cankers, isolated fasiculi of solid 
horny substance, of thready appearance, soft, analogous in their 
form to coarse brushes whose hairs are glued together. These 
isolated, still adherent, brushes are seen spreading towards the 
sole; they correspond with parts of the velvety tissue which 
have maintained their soundness in the midst of the diseased sur¬ 
face, and there continue to secrete healthy hoof. These horny 
growths are ordinarily multiple, and are of various shapes, often 
twisted, and give to the plantar surface a peculiar aspect, so 
much so, that their brushy masses sometimes retain the mud of 
the streets and are filled at their bases with a black and foetid sub¬ 
stance of an ugly appearance. 
When canker has arrived at a very advanced period, it is 
characterized by the deformity of the whole horny box, whose 
length and width is considerabl 3 r increased. The last of these 
conditions is a sure sign that the disease has spread under the 
wall of the quarters and of the heels, and has produced the com¬ 
plete separation of the bars from above and below. When per¬ 
cussed, the hoof at the heels gives a dull sound. The excessive 
length is only an indirect consequence of the disease, and is due 
to the fact that, so as to keep the animal at work, the walls are 
spared as much as possible by the blacksmith, so as to avoid the 
contact of the protruding parts with the ground. 
Physiological signs are almost entirely absent in canker. It is 
a curious fact that the sensibility which is generally highly in¬ 
creased in all affections of the foot, even in chronic diseases, 
remains always so obscure in canker that animals may be used for 
a long time without lameness, though the sub-horny tissues have 
over a large surface become quite unprotected. 
Complications .—Very frequently, canker is complicated by a 
disease of the skin, analogous to it, known as grease ; a disease 
which, if not entirely of the same nature, as admitted by Plasse, 
Megnin, &c., is closely related to it. It is often through this 
