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.

is subsequently destroyed by suppurative inflammation or by degenerative changes.

Encapsulation of a tumor imparts to it another clinical feature of great importance-mobility. This mobility, however, may be diminished or entirely prevented by the tumor being tied down by overlying firm structures, such as fascia, skin, and muscles. If the tumor is attached to the bone, as is the case in chondroma and osteoma, it is from the beginning immovable, and so remains. The question of mobility of a tumor is a valuable point in differential diagnosis, and is of special importance in the case of tumors of the breast. An adenoma of the mammary gland always remains movable, while in carcinoma of this organ the tumor almost from the beginning is so intimately connected with the surrounding tissues that the palpating finger receives an impression as though the tumor were grasped and firmly held in place. by the surrounding tissues. Some of the benign tumors-myxoma, chondroma, and some forms of fibroma-have received the reputation of being semi-malignant on account of their occasional recurrence after extirpation. A tumor is either benign or malignant: there is no connecting-link between them. The recurrence of a tumor after extirpation may be explained as follows: 1. The tumor was incompletely removed; 2. The primary tumor removed was malignant from the beginning; 3. A new tumor may develop in the scar of the operation-wound or in its immediate vicinity. Local recurrence after the removal of a benign tumor has been observed most frequently in cases of chondroma, myxoma, and fibroma-tumors which, from their clinical behavior as well as from the fact that their extirpation is sometimes followed by recurrence, have been regarded by many surgeons as suspicious or semi-malignant growths. We have reason to believe that in most cases local recurrence was due to imperfect removal. These tumors have a structure which renders their complete removal uncertain. Fibroma, for instance, is often surrounded by minute nodules, not large enough to be recognized by the naked eye, which are in histogenetic connection with the main tumor, and which, if the main tumor is removed by enucleation, remain in the tissues; from these nodules a recurrence takes place later. Such minute daughter-tumors are no evidence of the malignant nature of the primary tumor, as their histogenetic connection with the primary tumor can be demonstrated. The jelly-like structure of a myxoma renders the outline of the tumor irregular. Projections of the tumor between muscles and connective tissue are often overlooked, and if left in the bed of the tumor they certainly would give rise to local recurrence. Virchow years ago showed that chondroma originates not from the surface of a bone, but

in its interior. Surgeons seldom extend the operation far enough to include every vestige of the tumor, hence the frequency with which an enchondroma returns. If a tumor is removed completely and local recurrence takes place, it is more than probable that the primary tumor was of a malignant character, and that the relapse is the result of tissueproliferation from malignant cells left in the tissues. The clinical course of the tumor in such cases makes a more positive and reliable diagnosis than the surgeon and pathologist. Finally, a new tumor may grow from an additional congenital matrix of embryonic cells or from latent unutilized embryonic cells in the scar or in its immediate vicinity.

Malignant Tumors.-To the surgeon the most important clinical aspects of a malignant tumor are-1. Rapid growth; 2. Absence of limitation of the growth; 3. Local infection; 4. Regional infection; 5. General infection; 6. Frequency of recurrence after extirpation; 7. The intrinsic tendency of the tumor to destroy life. Rapidity of growth, as compared with that of benign tumors, belongs to malignant tumors as one of their salient clinical features. Some malignant tumors, particularly epithelioma of the skin, may remain in a latent stage for years before manifesting their true nature by rapid growth; these are, however, exceptional cases.

Absence of a limiting capsule is common to all malignant tumors. In some forms of sarcoma, to the naked eye such a capsule exists, but examination of the tissues adjacent to it under the microscope shows that tumor-cells have passed through and beyond the capsule into the connective tissue. The apparent capsule in such cases has been a source of deception to the surgeon who enucleates such a tumor under the belief that it is non-malignant. The absence of a proper limiting capsule brings the tumor-tissue in direct contact with the surrounding tissues, giving rise to local infection. The word "infection" as applied to the process of dissemination of malignant tumors has a different. significance than when the same term is applied to the origin and extension of acute and chronic infective diseases. In the latter case infection signifies the presence in the tissues of pathogenic microbes which exert their specific pathogenic effect upon pre-existing tissues. The word infection used to indicate the local, regional, and general dissemination of malignant tumors means the separation from the primary tumor of cells which migrate into the surrounding connective tissue, giving rise to local infection, or which are transported through the lymphatics of the region occupied by the tumor, causing regional infection; or, lastly, the malignant cells find their way directly or indirectly into the general circulation and become arrested in some distant part or organ as tumoremboli, resulting in general infection or general dissemination.

Local Infection.-Local infection of a malignant tumor is caused by the migration of tumor-cells from the place in which they were produced-that is, from the primary tumor-into the connective-tissue spaces in the immediate vicinity of the tumor. This migration of cells in all directions around the tumor results in a zone of tissue-infiltration by malignant cells, each cell establishing in its new location an independent centre of tumor-growth. As soon as a malignant cell has left its birthplace, it leads an independent existence and loses all histogenetic connections with the mother-tumor. It is the establishment of innumerable independent centres of tissue-proliferation in the zone of infiltration surrounding a malignant tumor that determines its rapid growth. Infection from a malignant tumor implies, therefore, only the invasion of adjacent or distant tissues by malignant cells; it is an infection by cells instead of by microbes, as is the case in the production of infective diseases. Another great difference in the two kinds of infection is this: in infective diseases the microbes act upon and alter pre-existing tissue-cells, while in tumor-growth the pre-existing tissue remains passive, the tissues of the tumor being derived exclusively from the tumor-cells. As a rule, local infection is much more pronounced and rapid in sarcoma than in carcinoma, hence greater rapidity of growth and larger size of the tumor.

Regional Infection.-Regional infection consists in the transportation of tumor-cells through the lymphatic channels some distance from the tumor to the lymphatic glands in the region occupied by the tumor. Familiar instances of regional infection are secondary carcinoma of the submental, submaxillary, and cervical glands in advanced carcinoma of the lip, and secondary carcinoma of the axillary glands in glandular carcinoma of the mammary gland. The regional dissemination of carcinoma is accomplished almost exclusively through the medium of the lymphatics. The carcinoma-cells, after finding their way into a lymphatic channel within or near the tumor, are transported by the lymphcurrent, and are arrested usually in the first lymphatic gland, which acts the part of a filter. The cell or cells establish here a new centre of growth, from which the tissues of the ensuing secondary carcinoma of the lymphatic gland are derived exclusively, the lymphoid cells taking no active part in the production of the tumor. From a gland thus infected tumor-cells again reach the lymphatic channel on the opposite side of the gland, and are taken up by the lymph-current and transported to the next lymphatic gland, where an additional centre of tumor-growth is established. By this progressive regional extension of the tumor the whole chain of glands between the primary tumor and the proximal termination of the lymphatic system becomes in