umour tissue next the shaft consists of a dense,
white, homogeneous material, from which there radiate into the softer
parts of the tumour, spicules, needles, and plates, often exhibiting a
fan-like arrangement (Fig. 151). The peripheral portion consists of soft
sarcomatous tissue, which invades the overlying soft parts. The
articular cartilage long resists destruction. The ossifying sarcoma is
met with most often in the femur and tibia, less frequently in the
humerus, skull, pelvis, and jaws. In the long bones it may grow from the
shaft, while the chondro-sarcoma more often originates at the
extremities. Sometimes they are multiple, several tumours appearing
simultaneously or one after another. Secondary growths are met with
chiefly in the lungs, metastasis taking place by way of the veins.

[Illustration: FIG. 146.--Periosteal Sarcoma of Femur in a young
subject.]

[Illustration: FIG. 147.--Periosteal Sarcoma of Humerus, after
maceration.

(Anatomical Museum, University of Edinburgh.)]

_Clinical Features._--Sarcoma is usually met with before the age of
thirty, and is comparatively common in children. Males suffer oftener
than females, in the proportion of two to one.

In _periosteal sarcoma_ the presence of a swelling is usually the first
symptom; the tumour is fusiform, firm, and regular in outline, and when
it occurs near the end of a long bone the limb frequently assumes a
characteristic "leg of mutton" shape (Fig. 146). The surface may be
uniform or bossed, the consistence varies at different parts, and the
swelling gradually tapers off along the shaft. On firm pressure, fine
crepitation may be felt from crushing of the delicate framework of new
bone.

[Illustration: FIG. 148.--Chondro-Sarcoma of Scapula in a man aet. 63;
removal of the scapula was followed two years later by metastases and
death.]

In _central sarcoma_ pain is the first symptom, and it is usually
constant, dull, and aching; is not obviously increased by use of the
limb, but is often worse at night. Swelling occurs late, and is due to
expansion of the bone; it is fusiform or globular, and is at first
densely hard, but in time there may be parchment-like or egg-shell
crackling from yielding of the thin shell. The swelling may pulsate, and
a bruit may be heard over it. In advanced cases it may be impossible to
differentiate between a periosteal and a central tumour, either
clinically or after the specimen has been laid open.

Pathologica