stages of the kinetic process. The kinetic process is divided into stages differently. Thus, Klebs makes four, while Strassburger describes the process as consisting of three stages: (1) Prophase; (2) metaphase; and (3) anaphase. During the first stage the nuclear chromatin arranges itself in the form of an oval mass. The metaphase is the stage of the equatorial crown when the nuclear spindle has an equatorial accumulation of chromatin fragments. During the last stage the nucleus and the protoplasm of the cell are divided into two symmetrical halves and complete the segmentation. Karyokinesis of the nucleus without division of the protoplasm of the cell results in multinucleated and

FIG. 7.-Cells from the epidermis of very young larva of newt (after Perso

skein; C, loose skein; D and E, mother-stars, seen from the posar field ane ap was the cat the F, mother-star from the side; G, migration of segments; r, daughterstars .and. about new polir fields in this protoplasm exhibits constriction Keske complete, with sight constriction of cell-body), 2, completed as of cod pro ...

th

giant cells. This incomplete karyokinesis frequently occurs cells of malignant tumors. The different karyokmore figeres are we shown in Figure 7. Cell-division by karyokinesis is called by 11 agamogenesis, in contradistinction to sexual reproduction, wh terms gamogenesis. In slowly-growing benign tumors new c added to the growth by karyokinesis; in stationary to now the c lost by degeneration are replaced by the same process, w nant tumors the karyokinetic process asstames great activ

in rapid growth and imperfect development of the cells. Karyokinesis in malignant tumors has received the careful attention of pathologists, and passes through the same phases as in the reproduction of normal tissue. In the centre of Figure 8 is seen a nucleus in which segmentation is nearly completed, while other nuclei represent incipient kinetic

FIG. 8.-Nuclear division in the epithelial cells of the skin in Paget's disease of the nipple; X 800 (after Karg and Schmorl). The deepest section of the picture represents, in the form of a small segment, the cutis infiltrated with leucocytes. After this follows the epidermis with its basal layer of cylindrical cells. The epithelial cells show different stages of nuclear division. Large nuclei are seen in the incipient stage of segmentation, surrounded by a light zone. In the centre of the field is a mass of chromatin threads in the stage of star-formation. Several chromatin loops have been separated from the dividing nuclear mass. The neighboring cells have been pushed sidewise. To the left and above, daughter-star with beginning constriction of the nuclear body. The threads of the achromatic figure are indicated. (Fixation and hardening in sublimate and alcohol; hæmatoxylin staining.)

changes. It is natural to suppose that such speedy and frequently imperfect karyokinesis would give rise to rapidly-growing, planless growths characterized by their early invasion of adjacent tissue, general dissemination, and an intrinsic tendency to destroy the life of the patient.

3

III. ANATOMY AND BIOLOGY OF TUMORS.

THE life-history of tumors is of great interest to the pathologist and of the utmost practical importance to the surgeon. The student must become familiar with the influences which favor and retard tumorgrowth before he can formulate a correct clinical distinction between the different varieties and outline a rational course of treatment. In the preceding sections we have studied the origin and growth of the parenchyma of tumors. We traced the tumor-cells to their original

FIG. 9.-Channel polypus of cervix uteri; X 50 (after D. J. Hamilton): a, fibro-cellular stroma of tumor; b, a gland of uterine mucous membrane; c, a channel; d, lining of columnar epithelium.

source and showed their manner of reproduction in the body. Before considering the biology of tumors it will be necessary to discuss a few of the more important points in their anatomy. The essential part of a tumor is its parenchyma; it is this which imparts to a tumor its anatomical characteristic and its clinical significance. The cells of a tumor are always limited by or imbedded in a stroma of connective tissue.

In Figure 9 is shown an adenoma of the cervical canal of the uterus in which the essential tumor-elements, columnar epithelial cells, are attached to and limited by a powerful stroma of connective tissue. This picture affords a good

a

illustration of the relation of the tumor-cells to the stroma in benign. tumors of the epiblast and hypoblast. In malignant and mesoblastic tumors the parenchyma appears as an interstitial product, the cells being enclosed on all sides by the stroma. The stroma or reticulum of a tumor is always derived from the mesoblast, and consists of some form of connective tissue in greater or lesser abundance (Fig. 10). In epiblastic and hypoblastic tumors the tissue reaches the tumor from the base; in mesoblastic tumors it furnishes a framework for the tumor on all sides.

FIG. 10.-Fibro-chondroma from capsule of knee; X 400 (after D. J. Hamilton): a, cartilage-cells;

b, the matrix.

Blood-vessels.-A tumor is nourished by the blood-vessels which supply the part or organ in which the tumor is located (Fig. 11). The blood-vessels constitute an important part in the structure, character, and life-history of a tumor. The vascularization of a tumor usually takes place by the formation of new blood-vessels from pre-existing vessels in its immediate vicinity by a process of budding. A more atypical blood-supply is sometimes procured by canalization of cells and the entrance of blood into pre-existing hollow spaces or into connectivetissue channels entering into communication with neighboring bloodvessels. Most of the tumors contain a complete vascular system; that is, one or a number of arteries enter it from the periphery and divide into smaller branches, which terminate in a network of capillaries from which the blood is returned to the general circulation through veins. The blood-vessels follow the connective tissue of the stroma, and in very soft and cellular tumors they often come in direct contact with its parenchyma (sarcoma). The structure of the walls of blood-vessels is often very defective, especially in soft and rapidly-growing sarcoma. Great vascularity of a tumor usually indicates rapid growth and imperfect development of the parenchyma-cells of the tumor. Perforation of the walls of the blood-vessels by the tumor-tissue, especially the veins, is often observed in malignant tumors, and leads to thrombosis or embolism, or both of these complications may occur in rapid suc

cession.

Lymphatic Vessels.-The existence of lymphatic vessels in tumors

was first discovered by Van der Kolk, who, as well as Krause, found them in carcinoma (Fig. 12). Lücke and Klebs attempted to inject the lymphatics of carcinoma of the lip before the extirpation of the tumor, but did not succeed in accomplishing the desired object. The benign growths are scantily, if at all, supplied with lymphatics. In carcinoma they are undoubtedly always present-a fact which explains on an

FIG. 11.-Blood-vessels of tumors (after Lücke): a, vascular injection in an osteoid chondroma; b, reticulum of veins from a sarcoma of the parotid; c, capillary network from a fibroma of the abdominal wall; d, same from a very vascular myeloid sarcoma of the lower jaw; e, vascular network from a carcinoma of the tonsil; f, alveolar vascular network from a carcinoma of the breast; g, injected preparation from a carcinoma of the lip.

anatomical basis the manner of regional dissemination which is so constantly observed during the clinical course of this tumor, irrespective of its anatomical location.

Nerves. But little is known concerning the innervation of tumors. In the myelinic variety of neuroma the production of new nerve-fibres has been demonstrated. The tenderness and the spontaneous pain