310 DISEASES OF THE HORSE’S FOOT 
nately refractory to treatment, showing always a tendency 
to spread to the other feet of the same animal, and often 
to the feet of other animals near enough to become infected, 
and always cured—when cured it is—by a treatment which 
may be summed up in two words as ‘rigid antisepsis.’ 
Other diseases, with points in common with this, have 
been directly proved to be due to a specific cause. Common 
regard for logic compels us to admit the same for canker. 
Fic. 134.—A Foot, THE SuBJECT OF CANKER, SHOWING DESTRUCTION 
oF THE Horny FrocG, anpD A FUNGOID-LOOKING HYPERTROFHY OF 
THE TISSUES BENEATH. 
Symptoms and Pathological Anatomy.—The symptoms of 
canker are seldom noticeable at the commencement of an 
attack. The disease is slow in its progress; for some time 
confines its ravages to the subhorny tissues unseen, and is 
quite unattended with pain. It is not observed, therefore, 
until considerable damage has been done, and the disease 
is far advanced. What is usually first seen is a peculiar 
softening and raising of the horn of the frog. The in- 
-fective material has set up a chronic inflammation of the 
