gluteal muscles and may occur as a complication of azoturia, or a lameness
of the hind limb that is usually due to a spavin.

It is very seldom necessary to give fractures of the ileum any special
care. If the animal is very lame, it should be given a narrow stall, and
placed in a sling until it can support its weight on the limb. The same
treatment is indicated in cattle. It is not advisable to breed a mare that
has had the ileum fractured. The bony enlargement that results from the
union of the broken ends of the bone may interfere with the passage of the
foetus through the pelvic cavity and cause difficult parturition.

[Illustration: FIG. 44.--Atrophy of the muscles of the quarter.]

LUXATION OF THE PATELLA, "Stifle Out."--This is a common accident in horses
and mules. Young, immature animals are more prone to displacement of the
patella than when mature. The displacement is usually upward or outward.
Outward displacement is comparatively rare.

_The causes_ of "stifle out" may be described as follows: The patella or
knee-cap rests on a pulley-like articular surface belonging to the inferior
extremity of the thigh-bone. The external lip of this articular surface is
smaller than the internal lip. The patella is held in place from above by
the heavy muscles of the anterior region of the thigh, and from below, by
straight ligaments that attach it to the leg-bone. If the retaining
structures mentioned become relaxed, the patella may, when the limb is
extended, become so displaced as to rest on the superior portion of the
external lip. Laxness of the muscles and ligaments in young animals is a
predisposing factor. Hard work that tires the muscles and causes them to
become relaxed, strains, unusual movements, as kicking in the stable and
slipping, may cause this accident. Congenital displacement results from