he organism, multiplying
indefinitely and destroying everything with which they come in contact.

Malignant tumours grow more rapidly than innocent tumours, and tend to
infiltrate their surroundings by sending out prolongations or offshoots;
they are therefore liable to recur after an operation which is
restricted to the removal of the main tumour. They are not encapsulated,
although they may appear to be circumscribed by condensation of the
surrounding tissues; they are rarely multiple at the outset, but show a
marked tendency to spread to other parts of the body. Fragments of the
parent tumour may become separated and be carried off in the lymph or
blood-stream and deposited in other parts of the body, where they give
rise to secondary growths. Malignant tumours tend to invade and destroy
the overlying skin or mucous membrane, and thus give rise to bleeding
ulcers; if the tumour tissue protrudes through the gap in the skin, it
is said to _fungate_. In course of time they give rise to a condition of
ill-health or _cachexia_, the patient becoming pale, sallow, feverish,
and emaciated, probably as a result of chronic poisoning from the
absorption of toxic products from the tumour. They ultimately destroy
life, it may be by their local effects, such as ulceration and
haemorrhage, by favouring the entrance of septic infection, by
interfering with the function of organs which are essential to life, by
cachexia, or by a combination of these effects.

The situation of a malignant tumour exercises considerable influence on
the rapidity, as well as on the mode, in which it causes death. Some
cancers, such as that known as "rodent," show malignant features which
are entirely local, while others, such as melanotic cancer, exhibit a
malignancy characterised by rapid generalisation of growths throughout
the body. Tumours that are structurally alike may show variations in
malignancy, according to their situation and to the age of the patient,
as well as to other factors which are as yet unknown.

In attempting to arrive at a conclusion as to the innocence or
malignancy of any tumour, too much reliance must not be placed on its
histological features; its situation, rate of growth, and other clinical
features must also be taken into consideration. It cannot be too
emphatically stated that there is no hard-and-fast line between innocent
and malignant growths; there is an indefinite transition from one to the
other. The possibility of