discovered,
Poulticing and antiseptic dressings were continued until August 16, when a
movable piece of the os pedis was found at the toe.

On August 25 this detached portion of the bone was removed, and turned out
to be the whole of the anterior margin of the os pedis, measuring 3-1/2
inches long, and varying in width from 1/2 inch to 1-1/2 inches. On
September 20 the mare was working without lameness.

3. FRACTURES OF THE NAVICULAR BONE.

Hidden within the wings of the os pedis, and protected as it is by its
tendinous covering and the yielding substance of the plantar cushion, the
navicular bone is even less liable to fracture than either of the other
bones of the foot.

The most common cause of fracture of the navicular is that of stabs or deep
pricks in the region of the point of the frog (see p. 216). Following that,
the next most common cause is violent injury. We thus find the navicular
bone fractured, together with one or both of the other bones of the foot,
when the foot is run over by a heavy vehicle. One such case is reported
by Mr. J.H. Carter, F.R.C.V.S., where the horse's foot was run over by a
tram-engine, in which the os pedis and the navicular were fractured in
several places.[A] A further case is on record where a sharp blow on the
front of the hoof was the cause. In this case the os pedis and other
structures were uninjured, but the navicular bone was fractured into three
large, and about half a dozen small, pieces.[B]

[Footnote A: _Veterinary Journal_, vol. xxxi., p. 246.]

[Footnote B: _Veterinarian_ for 1857, p. 73.]

Fractures of the navicular may occur, however, in which history of a prick
or of a violent injury is absent. See reported case below.

As with fractures of the os pedis and the os coronae, so with this exact
diagnosis is difficult--we may say almost impossible. With a history of
violent injury, however, some little regard may be paid to a continued heat
and tenderness of the foot, and a distinct inclination on the part of the
animal to go on the toe. Even when the fracture is the result of a prick,
and the bone is plainly felt with the probe, we still cannot be positive as
to fracture.

_Reported Case_.--'The animal was a Hungarian, a troop-horse in the 3rd
Hussars (G. 15). On November 22, 1881, on the march from Norwich to
Aldershot, the horse suddenly made a violent stumble, very nearly coming
on to his knees. The rider declared that he put his foot on a stone. The
accid