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(i.) They are manifestations of disordered overgrowth of some tissue of the body. In the
development of the body " we are aware of a delicate but effective power which controls, possibly
by way of the nervous system, the relations of tissues to one another " (W. G. McCallum) ; such a
mechanism is not operative in the case of tumours. The cells composing tumours have no regular
architectural arrangement, they never form organs that could be of any possible use, they pay no
regard to the rights of other organs, but burst their way recklessly through their boundaries and
their tissues, destroying their cells as they go. No tumour of glandular character has a duct nor are
its glands arranged in a such a way that it could discharge a secretion. No tumours are known to
be under the control of the nervous system, the only nerves they possess appearing to be accidental
inclusions. Nor are they subject to the normal conditions of nutrition, withstanding in an astonishing
manner starvation which produces wasting in the rest of the body.
(ii.) The cancer cells grow at the expense of the organism in which they serve no useful purpose.
(iii.) The growths are at first local. In many cases, as I shall point out later, it is apparently
some local factor, such as chronic irritation, which determines the appearance of Cancer. Moreover,
it is just this local character of Cancer in its early stages which in many cases gives us some hope of
success in treatment, if the disease can be diagnosed early enough.
(iv.) The growths are not encapsuled. Herein, as we shall see, lies the greatest difficulty in the
eradication of the disease. Cancerous growths scatter their isolated cells like spray in every direction,
or send out long threads of cells which insinuate themselves between the cells and fibres of the tissues
and even into the walls of the blood vessels and lymphatics. This method of spread, and the fact
that it is not possible with the means now at our disposal to distinguish with certainty a cancer cell
from a normal one are the reasons why it is a practical impossibility to determine in the living patient,
even at operation, the complete dispositions of the invading army whose far-flung outposts are so
cunningly hidden. Therefore—
(v.) Cancerous growths progressively invade the deeper parts.
(vi.) They readily undergo degeneration.
(vii.) They tend to become disseminated to distant parts of the body.
(viii.) They lead sooner or later to the death of the individual in the vast majority of cases
(hence the epithet " malignant " applied to all cancerous growths). This " malignant " character
of cancerous growths has been shewn by experimental work to be inherent in the cancer cells themselves,
which alone survive transference to a new host.
The rate of growth of cancer cells is very variable, and though in some forms it is extremely
rapid, even in the most rapidly invading forms the rate of growth is not to be compared with that of
the growing embryo. Nevertheless some investigators regard malignant growth as a reversion to
the habits of those primitive cells which, in their search for nourishment for the growing embryo,
eat their way into the maternal tissues and eventually open up the blood channels.
2. Its Distribution.—Cancer was formerly believed to be confined to the human race and to
the higher or so-called civilised races. Savages and other primitive races were thought to be exempt.
But extended study of the geographical and ethnological distribution of the disease tends more and
more to shew that no country, no district, no race, no nation can be considered as possessing immunity
from Cancer. Moreover it has been established beyond dispute that animals also suffer from this
disease, and not only those which come into frequent contact with man, but also purely wild animals,
and even deep sea fishes. The fact that in man Cancer is more liable to occur in old subjects than in
the young and that among animals few are allowed to attain old age may account, in part at least,
for the comparative rarity of Cancer among the latter. As regards the sex distribution of Cancer in
mankind there is a considerable excess of deaths of females over those of males. But it is important
to note that this excess is entirely due to malignant disease of the breast and generative organs ; in
most other parts of the body a considerable excess is recorded for males.
3. Its Cause.—There is no space here to describe all the numerous theories, plausible or
fantastic, which have been formulated to account for this peculiar and mysterious disease or group
of diseases. Though much valuable light has been thrown on the subject by recent researches one
can still assert, with confidence, that the true cause of Cancer remains undiscovered. It is, however,
of great importance that attention should be drawn to the following :—
(i.) Hereditary predisposition to Cancer in man has not been proved.
(ii.) There is no sound scientific evidence of the action of any particular article of food in predisposing
to or preventing the occurrence of Cancer.
(iii.) No known drug can prevent or cure Cancer.
(iv.) No scientific proof has been produced of danger from so-called " cancer houses " and
" cancer districts " in which the disease happens to have been unusually prevalent.
(v.) There is weighty scientific evidence against the supposition that Cancer is an infectious or
contagious disease.
The importance of chronic and prolonged irritation as a predisposing or determining factor in
Cancer has been established by modern experimental research, and this fact is of great practical
importance. But this factor alone is insufficient to determine the onset of the disease. The palm
of the hand, though constantly exposed to irritation of all kinds, has only once been recorded as the
seat of Cancer. Other tissues, however, shew a special tendency to develop Cancer, e.g., the tongue,
lips, skin of the face, inside of the cheeks, the lower part of the bowel and the neck of the womb.