EXPERIMENTAL LEUKAEMOGENESIS BY RADIATION 111 



DISCUSSION 



gray: Well, is it fair to say that in the thymic cases the depression of the bone-marrow 

 is playing a very important part? I got the impression from the differences in doses, 

 dose-rate and incident that, on the whole for these tumours, the more damage you were 

 doing (the more effective the radiation in the killing sense) the more tumours you obtain; 

 whereas in the other, the non-thymic ones, %vhere the incidence decreases with increasing 

 dose, if those were not involved, the bone-marrow depression would fall at the dose level 

 you use. This is, I think, something one would almost excpet if an initiating event were 

 in competition with cell destruction, because at these large doses you will be killing all 

 or a considerable number of cells. Is this a general way of lookmg at this correctly, or can 

 this be knocked down completely by the fact that I have taken a wrong interpretation of 

 bone- marrow damage? 



mole: The first table was of Upton's results not mine, but I would say that Berenblum's 

 experiences do not agree. He stepped up his dose to 400 r in order to get suflScient 

 initiation, and the kind of range that was covered in the table was 200^00 r. 



