267 



I may summarize the results of tlie experiuienls on 

 the cultivation of the chicken sarcoma cells by sayin^: 



1) Sarcoma cells behave as independent cell indi- 

 viduals, i. e. they are able to multiply even when 

 they are scattered and isolated in the culture nu'dium. 



2) Sarcoma cells are able to synthesise pro- 

 toplasm of their own fro m the s e r u m con- 

 stituents and dead muscular tissue. 



3) Sarcoma cells 1 1 (j u e f y the fibrin in t li e plas- 

 ma medium more e x t e n s i v e 1 y t h a u d o any 

 other normal tissue cells. 



These three biological characteristics of the sarcoma cells 

 sufficiently explain the aggressive, invasive and destructive 

 ability of these cells in vivo. 



In order to learn about the destructive mechanism of 

 the sarcoma cells in vivo, experiments were undertaken to 

 study the manner in which the sarcoma cells are able to 

 attack normal tissue cells and suppress their action. We 

 know of course that the malignant cells are able to suppress 

 the growth of the normal tissues, but the way they do so 

 we know absolutely nothing about. 



The interrelation of normal fibroblasts and sarcoma cells 

 was studied directly in the tissue cultures. To distinguish 

 between the normal fibroblasts and the sarcoma cells, the 

 latter were vitally stained. 



The experiments were made in the following way: To 

 cultures of sarcoma cells was added neutral red, trypan 

 red or Janus green in solutions 1:20.000. At the end of 21 

 hours incubation, the niigraicd sarcoma cells had readily 

 absorbed the stain; the cultures were then o])ened and by 

 means of a fine pipette, a little of the liquefied plasma 

 medium containing numerous vitally stained sarcoma 

 cells, was aspirated. The contents of the pipette were in- 

 troduced into a 24 hours old culture of fibroblasts I'belonging 

 to a strain V/^ year old, cultivated in I he Instiliilc of 

 General Pathology of Copenhagen). 



