abdominal wall. A rarer
variety is the ossifying chondro-sarcoma, which undergoes ossification
to such an extent as to be visible in skiagrams.

In primary sarcoma the treatment consists in removing the muscle. In the
limbs, the function of the muscle that is removed may be retained by
transplanting an adjacent muscle in its place.

_Hydatid cysts_ of muscle resemble those developing in other tissues.

DISEASES OF TENDON SHEATHS

Tendon sheaths have the same structure and function as the synovial
membranes of joints, and are liable to the same diseases. Apart from the
tendon sheaths displayed in anatomical dissections, there is a loose
peritendinous and perimuscular cellular tissue which is subject to the
same pathological conditions as the tendon sheaths proper.

#Teno-synovitis.#--The toxic or infective agent is conveyed to the
tendon sheaths through the blood-stream, as in the gouty, gonorrhoeal,
and tuberculous varieties, or is introduced directly through a wound, as
in the common pyogenic form of teno-synovitis.

_Teno-synovitis Crepitans._--In the simple or traumatic form of
teno-synovitis, although the most prominent etiological factor is a
strain or over-use of the tendon, there would appear to be some other,
probably a toxic, factor in its production, otherwise the affection
would be much more common than it is: only a small proportion of those
who strain or over-use their tendons become the subjects of
teno-synovitis. The opposed surfaces of the tendon and its sheath are
covered with fibrinous lymph, so that there is friction when they move
on one another.

The _clinical features_ are pain on movement, tenderness on pressure
over the affected tendon, and a sensation of crepitation or friction
when the tendon is moved in its sheath. The crepitation may be soft like
the friction of snow, or may resemble the creaking of new
leather--"saddle-back creaking." There may be swelling in the long axis
of the tendon, and redness and oedema of the skin. If there is an
effusion of fluid into the sheath, the swelling is more marked and
crepitation is absent. There is little tendency to the formation of
adhesions.

In the upper extremity, the sheath of the long tendon of the biceps may
be affected, but the condition is most common in the tendons about the
wrist, particularly in the extensors of the thumb, and it is most
frequently met with in those who follow occupations which involve
prolonged use or excessive s