350 GENERAL DISCUSSION 



100 and 1,000 times less than those which cause eqnally significant 

 damage to the cytoplasm, the latter damage without doubt exists and 

 plays an important negative role. 



Amongst the multifarious initial injuries to the cell, it is quite 

 possible that the destruction of the boundary cellular membranes plays 

 a part. Alexander and Passynsky attribute gi-eat significance to this, 

 although it seems to me that there is still much that is hypothetical and 

 speculative. 



The confused interaction of the initial reactions of the cell to radia- 

 tion leads to an extremely complex picture. 



We must attempt to separate, amonst the large number of initial 

 variations, those which give rise to important secondary biological 

 consequences and thus give to the radiation sickness of the cell, or of 

 its multicellular organism, its specific properties, and, in particular, 

 the difiicult reversibility which is so characteristic of it. 



The initial radiation injuries to the cell nuist be vitally important 

 under at least two conditions : in the first place if they damage unique 

 microstructures which occupy a key jjosition in biosynthesis, the loss 

 of which cannot be compensated by other apparently identical struc- 

 tures; in the second place, if the change which has occurred is irre- 

 versible and is reproducibly transmitted to daughter cells in the 

 process of ontogenesis, or from one generation to another, continuing 

 to give rise thereby to one and the same malfunction in this specific 

 synthesis. 



It is not difficult to see that these conditions are completely satisfied 

 l)y that cellular apparatus which, by determining the processes of 

 morphogenesis, secures the hereditable stal^ility of the biological 

 system ; I have in mind the cellular nucleus, or more accurately, its 

 genetic elements. 



On the contrary, the cytoplasm of the cell is characterized by a 

 multiple repetitiveness of its biochemical components, of identical 

 macromolecules and microstructures; by lability and by intensive 

 metabolic processes. In view of this it possesses the caj)acity for auto- 

 matic regulation by adaptive and i-eparative reactions in response to 

 damage inflicted from outside. 



We must therefore expect a much larger reversibility of radiation 

 injuries to the cytoplasm and their relative biological significance to 

 be less than is in general justified by the facts. 



Given such a functional approach the primary effect of the radiation 

 or the chain of initial changes (if this is a chain) must acquire a parti- 

 cular biological significance, starting with the element which already 

 affects the genetic structures of the cell. 



