472 DISEASES OF THE HORSE. 
INFLAMMATION OF THE HEELS WITH SEBACEOUS SECRETION 
(GREASE, OR CANKER). 
This is a specific affection of the heels of horses usually associated 
with the growth of a parasitic fungus, an offensive discharge from 
the numerous sebaceous glands, and, in bad cases, the formation of 
red, raw excrescences (grapes) from the surface. It is to be distin- 
guished (1) from simple inflammation in which the special fetid 
discharge and the tendency to the formation of “ grapes” are absent ; 
(2) from horsepox, in which the abundant exudate forms a firm, 
yellow incrustation around the roots of the hair, and is embedded 
at intervals in the pits formed by the individual pocks, and in which 
there is no vascular excrescence; (3) from foot scabies (mange), 
in which the presence of an acarus is distinctive; (4) from lymphan- 
gitis, in which the swelling appears suddenly, extending around the 
entire limb as high as the hock, and on the inner side of the thigh 
along the line of the vein to the groin, and in which there is active 
fever, and (5) from erysipelas, in which there is active fever (want- 
ing in grease), the implication of the deeper layers of the skin and 
of the parts beneath giving a boggy feeling to the parts, the absence 
of the fetid, greasy discharge, and finally a tendency to form pus 
loosely in the tissues without any limiting membrane, as in abscess. 
Another distinctive feature of grease is its tendency to implicate the 
skin which secretes the bulbs or heels of the horny frog and in the 
cleft of the frog, constituting the disease known as canker. 
Causes.—The predisposing causes of grease are essentially the same 
as those of simple inflammation of the heel, so that the reader may 
consult the preceding section. Though a specific fungus and bac- 
teria of different kinds are present, they tend mainly to aggravation 
of the disease, and are not proved to be essential factors in causation. 
Symptoms.—The symptoms vary according to whether the disease 
comes on suddenly or more tardily. In the first case there is a 
sudden swelling of the skin in the heel, with heat, tenderness, itching, 
and stiffness, which is lessened during exercise. In the slower forms 
there is seen only a slight swelling after rest, and with little heat or 
inflammation for a week or more. Even at this early stage, a slight, 
serous oozing may be detected. As the swelling increases, extending 
up toward the hock or knees, the hairs stand erect, and are bedewed 
by moisture no longer clear and odorless, but grayish, milky, and 
fetid. The fetor of the discharge draws attention to the part when- 
ever one enters the stable, and the swollen pastern and wet, matted 
hairs on the heel draw attention to the seat of the malady. If ac- 
tively treated, the disease may not advance further, but if neglected 
the tense, tender skin cracks open, leaving open sores from which 
vascular bleeding growths grow up, constituting the “ grapes.” The 
