98 



HOLLAENDER, StAPLETON AND BuRNETT 



this point (Giles and Riley, 1950) that there is an increased 

 response to X-rays with increasing concentration up to the 

 percentage of oxygen in air. Further increase of oxygen has 



40 60 80 100 



X-RAY DOSE IN KILOROENTGENS 



120 



Fig. 1. Comparative sensitivity of aerobic and anaerobic cells 

 irradiated in high and low oxygen-tensions. 



Curve B. Aerobic broth cells irradiated in oxygen-saturated 

 buffer. 



Curve B^. Aerobic broth cells irradiated in nitrogen-saturated 

 buffer. 



Curve GB. Anaerobic glucose cells irradiated in oxygen- 

 saturated buffer. 



Curve GB^. Anaerobic glucose cells irradiated in nitrogen- 

 saturated bujffer. 



Hollaender, Stapleton and Martin (1951), Nature, 167, 103. 



relatively little effect. The finding that 21 per cent oxygen 

 is the limiting concentration for the cells studied suggests 

 that this is a characteristic which may have been brought 



