CANCER.
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Colloid particularly involves the stomach, but is some- times seen in the omentum, intestines, and other parts. Epithelionia grows in con- nection either with the skin or a mucous surface, but by extension it may implicate any tissue. Its ordinary sites are the lower lip, the tongue, eyelids, cheeks, scrotum, pre- puce, labia, uterus, or blad- der. In exceptional cases in- ternal org-ans are involved.
Several parts may be at- tacked, either simultaneously, or usually in succession. In the latter case the original formation is said to be pri- mary, and subsequent growths are named secondary. Second- ary deposits are frequently observed in internal organs, being generally of the same variety as the primary growth, but scirrhus is often followed by encephaloid in internal or- gans. Malignant formations Epithelial Carcinoma. «. Separate cells; 6. Epithe.
usually show a marked ten- liai pearls. {Mtei BUiivth).
dency to spread, and to in- filtrate surrounding tissues, so that no line of demarcation can be observed ; in rare instances a kind of capsule forms around a cancerous growth.
Pathology. — Two very opposite views are entertained as to the nature and origin of cancer, viz : — i. That it is primarily a constitu- iional or blood- disease ox cachexia, of which the formation of malignant growths is but a local manifestation. 2. That it is in the first instance a local affection, produced by some direct irritation ; and that the blood is only changed secondarily, as the result of absorption of morbid materials from the primary growth. It is not at all impro- bable that both these theories are correct in different cases. Secondary growths arise in consequence of absorption by the blood-vessels and lymphatics, by which the cancerous material is conveyed to distant parts, especially those more immediately asso- ciated with the structure first affected. Neighbouring absorbent glands are very liable to become involved.
The stroma of cancer consists partly of the original cellular tissue, but is chiefly derived from hyperplasia of the connective- tissue elements. The cells originate in the proliferation of pre- existing cells; some pathologists are of opinion that they are only derived from epithelial structures, but others believe that they are
Fig. 14.
