Glandular carcinoma of the breast (after Klebs): a, epithelial layer of skin with long proliferating projections; b, carcinoma-tissue of epithelial cells and connective tissue c, the same with predominance of epithelial cells; d, milk-ducts.

A glance at Plate 2, Figures 2 and 3, and at Figures 24 and 25 will show the difference in the relation of epithelial cells in normal tis

FIG. 24.-Epithelioma of skin (after Thiersch): 1-2, ulcerated surface; 2-3, adjacent skin; a, hairfollicles with sebaceous glands made oblique by pressure from beneath; b, sweat-glands; c, epidermis, horny layer, which extends for some distance over ulcerated surface; d, avascular cell-masses of an epithelial nature, formed into irregular tubes by softening, only slightly attached to the stroma in which they are lodged, or separated from the walls of the alveoli during the hardening process in alcohol; e, connectivetissue stroma.

FIG. 25.-Columnar epithelioma of rectum (after Boyce): a, an epithelial process from skin of anus; b, a papillomatous gland-crypt. (Obj. 4 without eye-piece; logwood staining.)

1. Endothelioma hyalinum from capsule of submaxillary gland (after Klebs): a, stroma; b, smaller part of stroma; c, hyaline substance; d, cells. 2. Mucous membrane of large intestine of pig; X 350 (after Klein). The capillary blood-vessels cut in different directions surrounding the crypts are injected with carmine gelatin. vertical section through the epithelium covering the skin-epidermis; X 350 (after Klein): a, rete Malpighii, or rete mucosum; b, granular layer (Langerhans); c, stratum lucidum (Schrön); d, stratum corneum.

3. A

pria; in the latter instance they have found their way through the limiting membrane and have reached the underlying vascular mesoblastic tissues, where they have no legitimate physiological existence, and where they must be regarded pathologically as invaders.

It appears that in the subepithelial tissues a change takes place coincident with the senile changes in the tissues of persons advanced in life. Thiersch advanced the ingenious hypothesis that this change consists in a disturbance of the normal relations between the skin and the underlying tissues, this disturbance being caused by senile changes and resulting in a loss of resistance to the proliferating epithelial cells. There can be no doubt. that in the aged some such alteration of tissue takes place, permitting embryonic epithelial cells to part with their normal anchorage and to find their way by migration into the subjacent altered tissue, where they are no longer subject to the physiological laws which govern the reproduction and growth of normal epithelial cells, and where, in consequence of such aberration and lawless conduct, they produce a planless, functionless growth which invades all tissues, regardless of their anatomical

structure.

Sex. Statistics show on the whole that the male sex is more predisposed to tumor-formation than is the female. This difference. may be accounted for in part by the male sex leading a more active life, and being subjected more to the exciting causes which later in life become such a prominent feature in the etiology of tumors. Heredity affects both sexes equally, and the difference in the frequency with which tumors occur must therefore depend largely on occupation and habits of life. Of 1145 cases of tumor treated at the clinic of Berne during a period of twenty-five years, the males furnished 58.51 per cent. and the females 41.49 per cent. C. O. Weber gives the proportion of males to females as 64: 36. The proportion varies with the different forms of tumors. Carcinoma of the skin is much more frequent in the male than in the female, while in glandular carcinoma the reverse is the case. Moore in 1861 found in England one carcinoma patient to every 5846 men, and one female patient to every 2461 women. In women tumors are more prone to occur during the childbearing period of life than before and after. Carcinoma of the lip is common in men, but extremely rare in women. Of 696 cases of carcinoma of the lip collected by Lortet, 527 were men and 69 were women, the proportion of men to women being 7.6: 1. According to the writer's own observations, carcinoma of the stomach and the rectum is more frequently met with in males than in females. In the female, carcinoma of the breast and the uterus occurs probably more frequently than do malignant tumors of all the remaining organs.