Biological Effects of Penetrating Radiations 109 



differentiation which has sometimes resuhed in radiation car- 

 cinomata.'*^' '*'^' ^^^' Such growths can, however, be treated by 

 further radiation, if it is so deHvered that prohferative tendencies 

 of potential dividing cells are checked and the differentiation 

 processes promoted. ^"'^ 



The conditions under which the inhibiting action of radia- 

 tion on cell division is best achieved are beginning to be 

 understood, and it remains to determine the best physical condi- 

 tions for sterilizing cells by promoting differentiation. 



In this connection the combination of radiation with chemo- 

 therapy would seem a profitable field for future research, as 

 well as the effect of combining two or more different types of 

 radiation in the treatment of a single tumor. The problem 

 needs to be attacked from many aspects — hormonal, genetical, 

 chemical (including organizer substances), physical, and nutri- 

 tional — and upon its solution, in all probability, depends the next 

 substantial advance in the treatment of malignancy. 



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