TUMORS. 



387 



(Fig. 355). The connective tissue of the new site is then induced 

 to proliferate and form the cancerous stroma. If this transfer of 

 cells is only for a short distance, the process is called infiltration ; 

 if the distance is greater, metastasis. It appears, then, that meta- 

 stasis usually occurs through the lymphatics, as it is through them 

 that the natural extension of the carcinoma takes place. The cells 

 that gain entrance to the lymphatic vessels are most likely to be 

 arrested in the nearest lymph-node, giving rise, if they multiply, 



FIG. 356. 



Secondary carcinoma of a lymph-gland. (Ribbert.) Epithelial cells from the primary car- 

 cinoma have been carried by the lymph-current to the node, where they have been 

 arrested in the lymph-sinus. Here they have continued to proliferate, giving origin to a 

 secondary, or metastatic, nodule of carcinoma. 



to a secondary tumor within it (Fig. 356). These secondary tumors 

 in the lymph-nodes may, after a period of development, furnish 

 cells for a still wider metastasis. 



Metastasis through the lymphatics is not the only means by 

 which carcinomata may become generalized. They may infiltrate 

 the walls of bloodvessels, usually veins, and finally discharge 

 cells into the blood, giving rise to cancerous embolism with a gen- 

 eral diffusion of secondary nodules in the first capillary district 

 through which the blood is distributed. In this way multiple 

 carcinomata of the liver or lung are produced. The secondary 

 carcinomatous nodules usually resemble the primary tumor, espe- 

 cially as regards the character of the epithelium ; but the relative 

 amount of stroma is very frequently considerably less. A scirrhous 

 carcinoma may give rise to secondary nodules of medullary car- 

 cinoma. The distinction between the different varieties is, therefore, 

 more descriptive than essential. 



Carcinoma is apt to occasion the development of a cachexia in 

 the patient. The reason for this is probably to be sought in the 



