DISCUSSION 413 



blood-cell count in the peripheral cirpulation when plotted on multicycle semi- 

 logarithmic paper follows a straight line even over ranges of 5 X 10^ to 1 X 10*. 

 This relationship is then simply 



dw 



— = aw 

 dt 



and integrating, 



W = Ke"' 



where w is white-cell count per mm^, t is time, and a is a constant. 



Similar relationships exist for the white cell vs. time following x-irradiation 

 to the spleen. Thus, the results of beta radiation to the liver and of x-radiation to 

 the spleen in myelogenous leukemia have a striking similarity in effect on this 

 indicator. The most obvious common feature in the two conditions is the ex- 

 tremely high degree of vascularity of the organs irradiated. 



Friedell: 



At our laboratory in Cleveland we have been conducting some work on par- 

 titioning radiation by utilizing radioactive isotopes having selective localization 

 in the body. For example, colloidal Au^^^ will be deposited in the reticulo- 

 endothelial system and will therefore irradiate the liver and spleen primarily. 

 gj.90 Qj. p32 ^-yii i^g bone-seekers primarily. It is thus possible to irradiate these 

 two systems singly or in combination. We have found that the combination of 

 Au^^^ and P^^ results in marked synergism in the killing of albino rats. For 

 example, half the definitive dose of radiogold which will kill 20 per cent of the 

 animals, plus half a definitive dose of radiophosphorus which kills 20 per cent of 

 the animals, would, theoretically, result in a 20 per cent death rate. Instead, 

 a 60 or 70 per cent death rate is obtained. Analysis of these results is not easy, 

 but a relationship between separately irradiated systems has been suggested 

 previously. Jacobson's work on change in death rate by protection of the spleen 

 appears relevant to this problem. 



