escapes only when the sinus becomes surcharged or when,
during motion of the parts, the matter is forced to the surface.

_Symptoms._--These, of course, will vary according to the progress made
by the fistula. Following an injury we may often notice soreness or
stiffness of the front legs, and upon careful examination of the withers
we see small tortuous lines running from the point of irritation
downward and backward over the region of the shoulder. These are
superficial lymphatics, and are swollen and painful to the touch. In a
day or two a swelling is noticed on one or both sides of the dorsal
vertebrae, which is hot, painful, and rapidly enlarging. The stiffness of
the limbs may disappear at this time, and the heat and soreness of the
parts may become less noticeable, but the swelling remains and continues
to enlarge.

A fistulous ulcer of the poll may be first indicated by the opposition
which the animal offers to the application of stable brush or bridle. At
this time the parts are so sore and sensitive that there is some danger
that unless handled with the greatest care the patient will acquire
disagreeable stable habits. The disease in its early stages may be
recognized as a soft, fluctuating tumor surrounded by inflammatory
swelling, with the presence of enlarged lymphatic vessels and stiffness
of the neck. Later the inflammation of the surrounding tissues may
disappear, leaving a prominent tumor. The swelling, whether situated
upon the head or the withers, may open and form a running ulcer, or its
contents may dry up and leave a tumor which gradually develops the
common characteristics of a fibrous tumor. When the enlargement has
opened we should carefully examine its cavity, as upon its condition
will wholly depend our treatment.

_Treatment._--In the earliest stage, when there is soreness, enlarged
lymphatics, but no well-marked swelling, the trouble may frequently be
aborted. To do this requires both general and local treatment. A physic
should be given, and the horse receive 1 ounce of powdered saltpeter
three times a day in his water or feed. If the fever runs high, 20-drop
doses of tincture of aconite root every two hours may be administered.
The local application of cold water to the inflamed spot for an hour at
a time three or four times a day has often proved very beneficial, and
has afforded great relief.

Cooling lotions, muriate of ammonia, or saltpeter and water; sedative
washes, such as tinc