GENERAL DISCUSSION 341 



In recent years many competent radiobiologists have begini to recog- 

 nize the nnportant part played by the biological properties of living 

 organisms in tlie featnres of post-radiation processes. Thns, Rayevsky 

 stresses " the necessity of recognizing the physiological processes in 

 the cell in order to explain the biological action of the radiations". 

 Bacq recognizes the occnrrence of reciprocal reactions of the nerve 

 cells and hbres under radiation, although he supposes their subsequent 

 levelling (which in reality does not occur). Many rapid reflex mani- 

 festations in invertebrates have been shown. Summing up our data, 

 (j)art of which, concerning the rapid occurrence of histochemical and 

 functional destruction in the central nervous system, has been quoted 

 above) and the results of other authors, we suggest that evolutionary 

 biology, alongside an understanding of the radiophysical and radio- 

 chemical nature of j)rimary jjrocesses, obliges us to recognize a 

 change in the nervous system as the principal mechanism for the begin- 

 ning and development of radiation sickness of animals and of man. 



ALADJALOVA : I will coiicem myself with the question of the role in the 

 radiation eff'ect of intracellular surfaces, and intracellular structures, and 

 of the conservation of the damage by the investigation of ion transfer 

 in the insulated muscle of a frog. 



The data were obtained from measurements of the dielectric losses of 

 the tissue at audio and radio frequencies which served as the ion transfer 

 index. The irradiation was carried out in Ringer solution by X-rays in 

 doses from 5 to 100 kr; the dose-rate was 700 r per min. 



The direction of on movements in the muscular tissue after irra- 

 diation by X-rays (in the "closed" period with respect to the physio- 

 logical indices) is different from the direction in the stage of the mani- 

 festation of the biological effect. The variation of the dielectric losses 

 in the muscle even begins (see Fig. 1) during the irradiation and, from 

 the start, constitutes a fall. This can be explained by a reduction in the 

 number of ions in the tissue, which participate in the electro-conduc- 

 tivity. In the phase of the fall in transfer the excitability of the muscle 

 is maintained, moreover it is sometimes even increased — this is the 

 "concealed" period. 



However, after a certain dose which we shall call the "turning 

 point" (we speak here of doses of the order of 40 to 50 kr, for the 

 skeletal muscle of a frog) an increase in the dielectric losses in the 

 muscle occurs : the development of ionic processes of opposite direction 

 (polarity) is initiated. In this period the overall electric charge in the 

 system is increased due to the liberation of a large number of ions 

 from the surfaces of the membranes, evidently due to the beginning 



M 



