180 
MANUAL OF MODERN FARRIERY. 
should seldom he pared with a knife, but merely rasped 
down to a level surface. This is peculiarly applicable to 
the inner heel. The hind feet are seldom affected with 
corns, because they are stronger than the fore-feet, and 
less subjected to concussion ; and even where corns do exist, 
they do not produce lameness. 
CANKER. 
Canker consists of a separation of the horny substance 
from the sensible fleshy and bony portion of the foot, 
caused by the growth of fungus matter shooting up and 
occupying parts of, or the entire sole of the foot and frog. 
It is induced either by a puncture, bruise, corn, quittor, or 
thrush, more commonly proceeding from the latter than any 
other cause. It seldom attacks high-bred animals, being 
almost always confined to the heavy breed of cart and dray 
horses, which class seem to have a constitutional predisposi¬ 
tion to this complaint. Those which have previously had 
grease are peculiarly liable to canker, and especially those 
which have thick heels. Persons experienced in breeding 
have long ascertained that grease and canker follow certain 
blood, and have thus established the fact of these complaints 
being hereditary. Besides the hereditary predisposition of 
work-horses to canker, in order to give him foot-hold , it 
becomes necessary to raise the heels of the hinder feet 
so much that all pressure on the frog is done away with, 
which has the effect of destroying its functions, and con¬ 
sequently rendering it liable to disease. 
But canker is produced chiefly from the very ponderous 
shoes with which these horses are furnished, and the large¬ 
ness of the nails with which they are necessarily attached 
to the feet, together with the strain to which the animals 
are subjected in drawing and sustaining heavy weights. 
