The sarcoma includes as many varieties as there are tissues in this group, hence, Myxosarcoma, Liposarcoma, Gliosarcoma, Chondrosarcoma, Fibrosarcoma, melanosarcoma, Osteosarcoma. {123} GROUP OF TISSUES OF HIGHER FUNCTION. Myoma, of striped (rhabdomyoma) and smooth (leiomyoma) muscular tissue, Neuroma, of nerve tissue, Angioma, of blood-vessels, Lymphangioma, of lymphatics, Lymphoma (?), of lymph-gland tissue. EPITHELIAL GROUP. Epidermis: Callus, Corn, Keratosis, Horn, Onychoma. Epithelium of mucous membranes or glands: Struma (?), Adenoma, Cystoma. In the above varieties the growth of epithelium is more or less typical, a simple hyperplasia, either alone or combined with the new formation of fibrous tissue. Only the last three members of the series are tumors in the limited sense. CANCER. Cancer remains as an epithelial tumor, representing the atypical growth of cells resembling epidermis or the epithelium of glands and mucous membranes, extending into parts where epithelium is not found as a normal constituent. A new formation of connective tissue is usually associated with that of the epithelial cells. Numerous varieties of cancer are described, according to the physical and structural peculiarities of the tumor. The scirrhus and encephaloid of the earlier writers are now transformed into fibrous and medullary cancer. This change in name is due to the stress laid upon the predominance of the fibrous stroma as the usual cause for the hard, dense, scirrhous cancer, while an abundance of epithelioid cells in relatively large alveoli is present in the encephaloid, marrow-like, medullary variety. When the growth takes place from the skin or mucous membranes, the surface frequently presents numerous and usually arborescent papillæ or villi. The papillary cancers of the skin and the villous cancers of mucous membranes are thus distinguished. Cancerous growths of the skin and transitional membranes, often called epithelioma or cancroid, usually contain epithelioid cells resembling epidermis, and are therefore designated as epidermoid or pavement-celled cancer. The alveolar contents of certain cutaneous cancers are cells resembling those of the deeper layers of the rete mucosum, while those of other cancers of the skin resemble rather the epithelium of sweat-glands. Growths of the former character extend laterally, ulcerate early, and are known as superficial cutaneous cancer. They form one of the varieties of the so-called rodent ulcer. Cutaneous cancers, simulating in their structure a reproduction of the epithelium of sweat-glands, represent a variety of glandular cancer. The latter term is applied to cancerous growths which arise in glandular organs, with suggested resemblances of their cells to the gland-cells of the respective organ. {124} Cylindrical-celled cancer is frequently met with in those parts of which a cylindrical epithelium is a normal constituent.