Radiation and Regenerating Rat Liver 235 



used as a tracer to estimate nucleic acid synthesis. Table V 

 shows the results. At 2000 r, which was the dose used by 

 Dittrich and Hohne to demonstrate the decrease in sensitivity, 



Table V 



X-Ray Irradiation of Ehrlich Mouse Tumour 



Specific activity of DNA phosphorus as per cent of specific activity of inor- 

 ganic phosphorus. 



we could see no difference in the immediate or delayed effect 

 in DNA and RNA synthesis. In this tissue the uptake of ^^F 

 into the RNA is somewhat decreased by irradiation. At the 

 lower irradiation doses of 1650 r and 1500 r there is a sugges- 

 tion that the decrease of RNA synthesis is no longer found in 

 the "resistant" strain and there is, perhaps, a chance that we 



