GENERAL DISCUSSION 359 



The release of |)()tassiuin from the erythrocytes does not depeiul 

 upon the concentration of oxygen. I would be very glad if the effect of 

 oxygen could be studied for other processes as well. 



bacq: Certain effects which do not depend upon oxygen were pointed 

 out by Hollaender, for example the inhibition of mitosis in the neural 

 crest cells of the grasshopper. I myself have studied the effect in de- 

 creasing the resistance of the membranes of the skin. This effect has a 

 momentary latent period of the order of one second. 



Is there any other example of the independence of the radiation 

 effect from oxygen? 



EiDUS : I will quote facts concernhig the question of the universality 

 of the oxygen effect and the conditions for the destructive action of 

 oxygen. 



Some years ago we discovered that in one and the same protein 

 molecule there arise under radiation two kinds of concealed injury, 

 if we judge from the enzymatic activity. 



Some concealed injuries are converted into manifest injuries under 

 the action of heat, others under the action of oxygen. We suppose that 

 in both cases the effect is connected with the conservation of a part of 

 the absorbed energy in the long-lived excited state of the protein. 

 This has been confirmed in our joint work with Kayushin. 



It has been shown that the concealed injuries are connected with the 

 long conservation of unpaired electrons in the protein which are even 

 available in solution. Heating a solution of myosin to 20°C leads to 

 the inactivation of the molecules and simultaneously to the disappear- 

 ance of the unpaired electi'ons. 



The action of heat and oxygen are independent, that is, both these 

 agents act on different injuries. 



It is interesting that Powers in his work on biological objects arrives 

 at the same conclusions as to the existence of short- and long-lived 

 excited states, which are divisible into oxygen-dependent and oxygen- 

 independent as we concluded from our experiments with proteins; 

 in addition, his division even compares quantitatively with ours. A 

 comparison of the results of the experiments carried out by Powers 

 on dry objects, and by us on solutions is possible. This will allow us to 

 erect a bridge from our data to whole cells, to which our respected 

 President referred at the first session. 



The physical mechanism for damage both by oxygen and by heat is 

 so far not known for certain. But there are facts which throw light on 

 this question. An analysis of the literature and private data on the 



