THE RHYTHM OF OXIDATIVE PROCESSES 277 



long period. Radiation seems to iiit some link of rhythmical activity 

 connected with oxidative processes of rapidly manifested effect. 



Restoration of rhythmic activity in time does not coincide with that 

 of the abiUty to ntilize oxygen. Thongh both processes are interrelated 

 to some extent, this interrelation is neither rigid, nor simple. 



It is very interesting that rhythmical fluctnations of oxygen content 

 can be revealed under certain conditions in isolated pieces and sections 

 of organs of a homoiothermal animal, for example, in a liver. 



The same phenomena are found in plants and even in a population 

 of yeast cells. 



Distinct rhythmical changes in free oxygen content and disturbances 

 of this rhythmical activity were obtained with the roots of Vicia faha 

 seedlings. Under normal conditions, with an appropriate electrode in- 

 sertion, not very regular and ordered changes in the level of oxygen 

 content are clearly revealed. In some cases periods with a great ampli- 

 tude of the order of 1 per min or even 1 per 1 -5 to 2 min and those of 

 the order of 10 per min appear. 



When the accumulated radiation dose reaches some hundreds of r, 

 an appearance of a kind of inhibition of this rhythm, arising almost 

 immediately after irradiation is very characteristic (Fig. 6). In the 

 process of irradiation this rhythmic activity in the form of irregular 

 splashes is manifested from time to time by either a small or a very 

 sharp and considerable change in the level of oxygen content. By the 

 end of irradiation with a dose of 10,000 r, (which is not an excessive 

 one for plants), a practically straight line appears instead of a curve of 

 dentate character. The change takes place 1 hr after exposure, while 

 after more than 2 hr the absence of any oscillation is still more clearly 

 manifested. Thereafter a continuous drop of the total level of free 

 oxygen content takes place. So, prior to irradiation this level amounts 

 to 6 to 7 "units". By the end of the irradiation it has fallen to 3-5 units. 

 After 3 hr with the most smooth character of the curve and a complete 

 absence of the rhythm this level becomes 2. It then starts to be gradu- 

 ally restored. 



It can be seen that 7 hr after exposure the rhythmical character of 

 the curve is recovered ; after 24 hr it is manifested rather distinctly, 

 while after 2 to 3 days rhythmical activity is clearly stimulated. 

 Amplitude and, above all, frequency of the rhythm, are much greater 

 than they were prior to exposure. 



A decrease of the total level of free oxygen at the moment of the most 

 practically complete smoothing of the rhythm does not contradict the 

 facts mentioned above and observed in the tissue of the central nervous 

 system of a living expei'imental animal. In this case the level of free 



K 



