uefaction which result in the formation of cystic
cavities in the interior of the tumour. The colour depends on the amount
of blood in the tumour, and on the presence of the products of
degeneration.

The blood vessels are usually represented by mere chinks or spaces
between the cells. This peculiarity accounts for the facility with which
haemorrhage takes place into the substance of the tumour, the persistence
of the bleeding when it is incised or ulcerates through the skin, and
the readiness with which the sarcomatous cells are carried off and
infect distant parts through the blood-stream. Sarcomas are devoid of
lymphatics, and unless originating in lymphatic structures--for example,
in the tonsil--they rarely infect the lymph glands. Minute portions of
the tumour grow into the small veins, and, becoming detached, are
transported by the blood-current to distant organs, where they are
arrested in the capillaries and give rise to secondary growths. These
are most frequently situated in the lungs, except when the primary
growth lies within the territory of the portal circulation, in which
case they occur in the liver. The secondary growths closely resemble the
parent tumour. Sarcoma may invade an adjacent vein on such a scale that
if the invading portion becomes detached it may constitute a dangerous
embolus. This may be observed in sarcoma of the kidney, the growth
taking place along the renal vein until it projects into the vena cava.

[Illustration: FIG. 55.--Recurrent Sarcoma of Sciatic Nerve in a woman
aet. 27. Recurrence twenty months after removal of primary growth.]

In its growth, a sarcoma compresses and destroys neighbouring parts,
surrounds vessels and nerves, and may lead to destruction of the skin,
either by invading it, or more commonly by causing sloughing from
pressure. Inflammatory and suppurative changes may take place as a
result of pyogenic infection following upon sloughing of the overlying
skin or upon an exploratory incision. Once the skin is broken the tumour
fungates through the opening. Sarcomas vary in malignancy, especially as
regards rapidity of growth and capacity for dissemination. Certain of
them, such as the so-called "recurrent fibroid of Paget," grow
comparatively slowly, and are only malignant in the sense that they tend
to recur locally after removal; others--especially the more cellular
ones--grow with extreme rapidity, and are early disseminated throughout
the body, resembling in