TRANSPLANTATION OF TUMORS 399 



In comparing the conditions which influence the transplantation of normal 

 tissues and of tumor tissues, we conclude that in both of these processes the 

 relations between organismal differentials of host and transplant play a similar 

 role, but that various factors of a secondary nature may obscure the signifi- 

 cance of the organismal differentials, and this applies particularly to tumor 

 growth. The conditions determining the growth of transplanted tumors include 

 the factors which control the growth of normal tissues, as well as other 

 factors which are specific for tumor tissue, such as the intensified growth 

 momentum, the possibility of increasing this growth momentum still further, 

 and the potentiality to undergo special adaptations in the course of serial trans- 

 plantations. In the analysis of tumor growth and tumor transplantations, it 

 is necessary to separate these various factors as much as is possible at the 

 present time. 



