e seat of lacerations or sprains resulting
from violent efforts or sudden jerks.

_Cause._--The injury may be considered serious or trifling, according to
the circumstances of each case as judged by its own history. Among the
predisposing causes are a long, thin fetlock and a narrow knee or hock
as viewed from the side, with the flexor muscles tied in just below the
joint. The longer and more oblique the pastern the greater is the strain
on the flexor tendons and suspensory ligaments; hence a low quarter, a
toe calk, and no heel calks, or a thin calk placed at the tip under the
toe, and leaving the quarters long abnormally stretches the back tendons
and causes a great strain upon them just before the weight is shifted
from the foot in locomotion. In runners and hunters the disease is
liable to be periodic. In driving horses it is most common in well-bred
animals of nervous temperament. Draft horses suffer most frequently in
the hind legs.

_Symptoms._--The injury is readily recognized by the changed aspect of
the region and the accompanying local symptoms. The parts which in
health are well defined, with the outlines of the tendons and ligaments
well marked, become the seat of a swelling, more or less developed, from
a small spot on the middle of the back of the tendon to a tumefaction
reaching from the knee down to and even involving the fetlock itself. It
is always characterized by heat, and it is variously sensitive, ranging
from a mere tenderness to a degree of soreness which shrinks from the
lightest touch. The degree of the lameness varies, and it has a
corresponding range with the soreness, sometimes showing only a slight
halting and at others the extreme of lameness on three legs, with
intermediate degrees.

The lameness is always worse when the weight is thrown on the foot and
is most marked toward the end of the phase of contact with the ground.
Either passive irritation of the leg or turning the animal in a circle
causes pain as in diseases of the joints. Sometimes the horse likes to
get the heels on a stone or some elevation so as to relieve the weight
from the flexor tendons. Finally, in cases of long standing, a
shortening of the tendons occurs, resulting in the abnormal flexion of
the foot known by horsemen as "broken down," or a more upright position
of the foot may follow, producing perhaps knuckling or the so-called
clubfoot.

_Prognosis._--It may be safely assumed on general principles that a leg