2()0 



blasts. This is probably nol clue lo (he luxuriant growth 

 of the maglinanl cells in the cultures, but because of some 

 of the peculiarities of the malignant cells. It is without 

 doubt the liquefying power of the sarcoma cells which has 

 deprived the fibroblasts of their stroma, and scattered these 

 cells. The proteolytic power of the sarcoma cells may 

 therefore also play an important role in the mechanism 

 of the malignity. That the sarcoma cells actually are able 

 to disintegrate entirely a normal complex tissue, was de- 

 monstrated by other experiments. 



To a culture of a fragment of intestine of a chicken em- 

 bryo (20 days old), was added a small piece of sarcomatous 

 tissue of the Rous sarcoma; the intestinal fragment had 

 been cultivated in vitro for about a month, and intestinal 

 epithelium had grown all around the fragment, so that 

 it looked like an epithelial cyst. The cyst or 'intestinal 

 organism ", and a piece of sarcomatous tissue was placed 

 side by side in one culture and allowed to grow in that way. 

 A few days later, the intestinal cyst had perfectly disap- 

 peared and the sarcomatous tissue was left. The effect of 

 the sarcoma cells on the '•intestinal organism" was a perfect 

 disintegration of its cellular elements. The stroma of the 

 tissue has been digested by the sarcoma cells, and the 

 cells falling apart, could now be observed floating around 

 in the liquefied medium. These scattered cells are no longer 

 able to reunite or proliferate. 



These biological characters observed for the malignant 

 sarcoma cells in vitro, are undoubtedly responsible for theij' 

 destructive, parasitic character in vivo. 



^\e could imagine that the destructive process of the 

 sarcoma cells in vivo would be as follow^s. First the stroma 

 binding the cells together is liquefied. Consequenth^ reor- 

 ganisation cannot take place as long as the lytic agent, the 

 sarcoma cells, is present and because the fixed tissue cells 

 are deprived their fibrin stroma. Besides we have learned 

 that the scattered and isolated tissue cells are not able to 



