110 



H. Laser 



hydrogen; nor has it been confirmed by Dale and Russell 

 (1956). 



Furthermore, the involvement of haematin compounds fol- 

 lows from experiments with Escherichia coli (Fig. 2), in which 

 the influence of irradiation on respiration and on aerobic acid- 

 production of washed non-growing cells has been measured. 



kr 



Fig. 2. Percentage inliibition of respiration and anaerobic glycolysis 

 of washed suspensions of Esch. coli irradiated in air with increasing dose 



of X-rays. 



The rate of oxygen uptake in the presence of glucose was 

 progressively inhibited with increasing doses of X-rays, up to 

 a maximum of approximately 65 per cent at 5,000 r. The 

 remaining 35-40 per cent respiration was found to be cyanide- 

 insensitive and could not be further reduced by increasing the 

 X-ray dose sixfold, although reproduction was progressively 

 more inhibited. Inhibition of anaerobic acid production 

 (after aerobic irradiation) follows a different course from that 

 of respiration but reaches the same plateau at about 30 kr. 

 Here, again, the remaining anaerobic acid production was 



