302 



RADIATION BIOLOGY 



multiplication and 58 per cent inhibition of respiration (Tables 5-6 and 

 5-7) . The respiration of the bacterial cells is more resistant to the action 

 of ionizing radiations when washed cells suspended in water are irradiated. 

 Under these conditions irradiation with 6000 r has no effect on the endog- 

 enous respiration, whereas the respiration in the presence of acetate and 

 aspartate is inhibited 35 and 10 per cent, respectively (Barron and 

 Gasvoda, 1949b). 



Table 5-6. Effect of X Rays on the Growth of Corynebacterium creatinovorans 



Irradiated in Its Own Medium 

 (Growth measured as increase in turbidity 6 hours after irradiation) 



Table 5-7. Effect of X Rays on Respiration of Corynebacterium creatinovorans, 



Irradiated in Its Own Culture Medium 



(Values give O2 uptake in 5 hours) 



The effect of ionizing radiations on cell multiplication in yeast was 

 found to depend on the degree of ploidy by Latarjet and Ephrussi (1949) 

 and by Zirkle and Tobias (personal communication). According to these 

 very interesting findings there is only 10 per cent "survival" on irradia- 

 tion of haploid cells with 4000 r ("survival" is defined as the power of the 

 cells to divide when placed in a culture medium), whereas there is no 



