418 DISEASES OF THE HORSE. 
subject to the disease, except in wet, marshy districts, than are the 
horses used in cities and towns. 
Causes.—The most common cause of thrush is the filthy condition 
of the stable in which the animal is kept. Mares are more liable to 
contract the disease in the hind feet when filth is the cause, while 
the gelding and stallion are more liable to develop it in the fore 
feet. Hard work on rough and stony roads may also induce the 
disease, as may a change from dryness to excessive moisture. The 
latter cause is often seen to operate in old track horses, whose feet 
are constantly soaked in the bathtub for the purpose of relieving 
soreness. Muddy streets and roads, especially where mineral sub- 
stances are plentiful, excite this abnormal condition of the frog. 
Contracted heels, scratches, and navicular disease predispose to 
thrush, while by some a constitutional tendency is believed to exist 
among certain animals which otherwise present a perfect frog. 
Symptoms.—At first there is simply an increased moisture in the 
cleft of the frog, accompanied with an offensive smell. After a time 
a considerable discharge takes place—thin, watery, and highly offen- 
sive, changing gradually to a thicker puriform matter, which rap- 
idly destroys the horn of the frog. Only in old and severe cases is 
the patient lame and the foot feverish—cases in which the whole 
frog is involved in the diseased process. 
Treatment.—Thrushes are to be treated by cleanliness, the removal 
of all exciting causes, and a return of the frog to its normal condi- 
tion, As a rule, the diseased and ragged portions of horn are to be 
pared away and the foot poulticed for a day or two with boiled tur- 
nips, to which may be added a few drops of carbolic acid or a handful 
of powdered charcoal to destroy the offensive smell. The cleft of 
the frog and the grooves on its edges are then to be cleaned and well 
filled with dry calomel] and the foot dressed with oakum and a roller 
bandage. If the discharge is profuse, the dressing should be changed 
daily; otherwise it may be left on two or three days. Where a con- 
stitutional taint is supposed to exist, with swelling of the legs, grease, 
etc., a purgative, followed by dram doses of sulphate of iron, re- 
peated daily, may be prescribed. In cases where the growth of horn 
seems too slow a Spanish-fly blister applied to the heels is often fol- 
lowed by good results. Feet in which the disease is readily induced 
may be protected ’in the stable with a leather boot. If the thrush is 
but a sequel to other disease, a permanent cure may not be possible. 
CANKER. 
Canker of the foot is due to the rapid reproduction of a vegetable 
parasite. It not only destroys the sole and frog, but, by setting up a 
chronic inflammation in the deeper tissues, prevents the growth of 
