cent and overlying tissues.

Ray treatment is not to be looked upon as a rival but as a powerful
supplement to the operative treatment of cancer.

VARIETIES OF CANCER

The varieties of cancer are distinguished according to the character and
arrangement of the epithelial cells.

The _squamous epithelial cancer_ or _epithelioma_ originates from a
surface covered by squamous epithelium, such as the skin, or the mucous
membrane of the mouth, gullet, or larynx. The cancer cells retain the
characters of squamous epithelium, and, being confined within the lymph
spaces of the sub-epithelial connective tissue, become compressed and
undergo a horny change. This results in the formation of concentrically
laminated masses known as cell nests.

The clinical features are those of a slowly growing indurated tumour,
which nearly always ulcerates; there is a characteristic induration of
the edges and floor of the ulcer, and its surface is often covered with
warty or cauliflower-like outgrowths (Fig. 58). The infection of the
lymph glands is early and constant, and constitutes the most dangerous
feature of the disease; the secondary growths in the glands exhibit the
characteristic induration, and may themselves break down and lead to the
formation of ulcers.

[Illustration: FIG. 58.--Epithelioma of Lip.]

Epithelioma frequently originates in long-standing ulcers or sinuses,
and in scars, and probably results from the displacement and
sequestration of epithelial cells during the process of cicatrisation.

The _columnar epithelial cancer_ or _columnar epithelioma_ originates in
mucous membranes covered with columnar epithelium, and is chiefly met
with in the stomach and intestine. As it resembles an adenoma in
structure it is sometimes described as a _malignant adenoma_. Its
malignancy is shown by the proliferating epithelium invading the other
coats of the stomach or intestine, and by the development of secondary
growths.

_Glandular carcinoma_ originates in organs such as the breast, and in
the glands of mucous membranes and skin. The epithelial cells are not
arranged on any definite plan, but are closely packed in irregularly
shaped alveoli. If the alveoli are large and the intervening stroma is
scanty and delicate, the tumour is soft and brain-like, and is described
as a _medullary_ or _encephaloid cancer_. If the alveoli are small and
the intervening stroma is abundant and composed of dense fibrous tissue,
the tumour is h