368 THE PROLIFERATION OF CANCER 



site. We have seen amoeboid movements in cancer- 

 cells in response to alkaloids, and possibly this may 

 assist in the infiltration of vessels and tissues and so 

 predispose to metastasis. A striking fact known about 

 secondary growths is that in the arrangement of the 

 cells they resemble the primary ones. We think that 

 this can be explained only by embolism. If a second- 

 ary growth in another organ was a fresh cancer, it 

 is difficult to imagine how it could possibly resemble 

 the primary ones in the arrangement of the cells. 

 Metastases practically only occur in the later stages of 

 carcinoma when the lymphatics have been extensively 

 invaded. In benign growths one rarely if ever sees the 

 vessels invaded by cells, and presumably this is the 

 reason why secondary tumours do not follow. The 

 extensive researches which have been done by others 

 in transplanting tumours in mice have thrown con- 

 siderable light on the nature of secondary growths. 

 In transplanting a tumour from one animal to another, 

 it seems to us that one is in reality producing a secondary 

 tumour. Now, to effect this, as is well known, it is 

 necessary that the cells of the tumour should be alive; 

 the transplanting of dead cells will not cause a second- 

 ary growth. This knowledge harmonises with our 

 suggestions as to the cause of cancer. If one inoculates 

 an animal with dead cells, although the organisms of 

 putrefaction may be present among them, the remains 

 of the dead cells are soon removed from the inoculation 

 site and the production of augmented auxetic must 

 cease. Normal healing will take place before the 

 putrefactive organisms have had time to restart and pro- 



