GENERAL DISCUSSION 353 



processes of radiation damage. It seems to me that in order to reply to 

 this question, it is necessary, with maximum clarity, to emphasize the 

 distinction between the two types of radiation damage. 'J\) the first 

 type ^ye must refer various injuries which are restricted to the cell 

 which has received the radiation, has had its structure, metabolism 

 and function destroyed and, in the extreme case, has been })rought to 

 death: these injuries are not transmitted to its descendants. To the 

 other type belong such injuries as do not lead to the death of the cell, 

 but are reduplicated through many cellular generations. We are dealing 

 here with a change in genetic information. 



I cannot understand why the attention of radiobiologists in particu- 

 lar, and at this symposium, is to such a great extent concentrated on 

 injuries of the first type, and why so little attention is devoted to in- 

 juries of the second type. In particular, in the general integration of 

 radiation damage processes presented here by Kuzin, there is not even 

 a place for changes in the code of the genetic information. This unequal 

 distribution of attention between injuries of the first and second types 

 is the less understandable in that injuries of the second type are not 

 only incomparably more interesting from the general biological and 

 evolutionary point of view, but also have much more practical value 

 than injuries of the first type. 



Turning now to the problem posed by Bacq, I would like to say that 

 one can destroy or damage a cell by many methods, and therefore 

 various chemical reactions or series of reactions may evidently be res- 

 ponsible for these injuries at the chemical level. As far as the variations 

 which are reproducible in the descendants of the irradiated cell are con- 

 cerned, then it is possible that there exists here some general mecha- 

 nism for the variation of the genetic code. It is very probable that in 

 all cases of the occurrence of mutations, under the action of diverse 

 factors (ionizing radiation, chemical mutagens, etc.), the primary 

 mechanism for the variation of the code is one and the same. It seems 

 to me, partly intuitively — I have no proof of this — that we are speaking 

 here not of general chemical reactions but of a certain common, ele- 

 mentary, physical action the mechanism of which is still not yet com- 

 pletely clear ; as unclear, by the way, as the mechanism of coding and 

 decoding of the genetic information itself. 



It would be of great interest to me to know what biologists think 

 about this question. 



trincher: Erythrocytes, suspended in a physiological solution which 

 contained blood serum, proved to be the more radiosensitive the lower 

 the concentration of the serum proteins. This phenomenon — a protective 



