DISCUSSION 



DISCUSSION 



Dr. Vogel: If your hypothesis is correct, how do you account for tlic lack of leuk- 

 aemia production that Dr. Loutit just reported in Dr. Mole's experiments — that is, 

 when the radiation dose level was low, he reported that in ten months there were 

 no leukaemias; also in Dr. Kaplan's work. I believe fractionating four times increased 

 the leukaemia rate. How does your theory account for these marked changes in 

 leukaemia appearing in mice? 



Dr. Metcalf: We do not really know, since the only type of irradiated mouse we 

 worked with has either received a single dose or three fractionated doses. Both 

 spreading the irradiation out over a long period and giving intense doses of some 

 thousands of roentgens locally to the thymus failed to induce leukaemia and we 

 wondered whether, since this L.S.F. production was radio-sensitive, we were either 

 wiping it out completely in the case of the very large doses, or keeping it suppressed 

 by a continuous small dose. However, we have not checked up on thymus function 

 in mice of that type. 



29 



