DIFFUSION BY MEANS OF CONTAGIOUS JUIfiES. 353 



instance encroach upon the walls of the veins, so that 

 they become really cancerous, and after a certain time 

 the cancer either grows directly through the walls into 

 the vessel and there continues its course, or a thrombus 

 forms at the point, which invests the cancerous plug in 

 a greater or less degree and into which the mass of can- 

 cer grows. Here, therefore, we see a diffusion of the 

 disease may possibly take place in two different manners, 

 but the diffusion of corpuscular elements only in one, 

 when, namely, an irruption ensues into the veins. An 

 absorption of cancer-cells by means of the lymphatics 

 cannot indeed in itself be ranked amongst impossibilities 

 but at all events this much is certain, that no propaga- 

 tion of the disease can take place until the lymphatic 

 glands have in their turn undergone a complete cancer- 

 ous transformation, and similar masses of cancer push on 

 their growth from them into their efferent vessels. In 

 no case can a peripheral lymphatic vessel sweep along 

 into the blood the cells of the cancer so simply as it does 

 the fluid parts ; this is only conceivable and possible in 

 the case of the veins. But even in that case there is not 

 the slightest probability that noxious matters are fre- 

 quently diffused by their means, and for the simple rea- 

 son that the metastases of cancer very frequently do not 

 correspond with those with which we have become ac- 

 quainted as occurring in embolia. The usual form of 

 metastatic diffusion in cancer follows rather the direction 

 of the secreting organs. The lungs, as is well known, are 

 much more rarely invaded by cancerous disease than the 

 liver, not only after gastric and uterine, but also after 

 mammary cancer Which would necessarily rather produce 

 cancer in the lungs, if it were anything corpuscular which 

 was conveyed away, became stagnant and gave rise to a 

 new eruption of the disease. The manner in which the 

 metastatic diffusion takes place seems, on the contrary. 



