318 
MANUAL OF MODERN FARRIERY. 
various diseases to which it is applicable. Blisters act or? 
the principle that two intense states of inflammation cannot 
exist in contiguous parts of the system at one time ; therefore 
we apply some acrimonious substance to the skin to induce ex¬ 
ternal inflammation, to draw away that existing in some deeper 
contiguous parts. Upon this principle we apply a blister to 
the side in cases of inflammation of the lungs; for inflam¬ 
mation of the bowels, we blister the belly; the legs are 
blistered for that of the cellular substance surrounding the 
sheaths of the tendons ; and for inflammation of the navi¬ 
cular joint, we make the coronet or heel the medium of 
operations. Besides their use in inflammation, blisters are 
useful in increasing the activity of the vessels contiguous to 
the places where they are applied. In cases of strangles, 
for example, a blister is used to induce earlier suppuration. 
Such is the power of blisters, that they will excite the 
absorbents to greater energy, and by this means they will 
carry away tumours, and callous, and even bony substances. 
In the application of blisters there is some nicety re¬ 
quired to determine when a stronger or weaker one must 
be applied ; whether by long-continued, or sudden and 
violent action, the desired effect is most likely to be pro¬ 
duced. In inflammatory cases, strong blisters will be found 
best; but in old and long-seated tumours and swellings, 
milder means must be adopted. 
It is necessary to prepare the skin of the horse for a 
blister, by clipping off or shaving closely all the hair of the 
part where it is to be applied. The best composition for a 
blister is Spanish flies, lard, and resin, in the proportions for 
which we have given a recipe at page 59. This should be 
thoroughly rubbed in, otherwise it will not rise. After the 
application of a blister the head of the horse must be tied 
up for at least two days, to prevent him from disfiguring 
