RADIATION DEATH IN MAMMALS 



tissue of the body. The third dose range is characterized by a rapid reduc- 

 tion of survival time of the irradiated animals. The mechanism producing 

 the final effects in this dose range is apparently completely different from 

 the mechanism prevailing in the second dose range. 



In the fourth dose range animals die with symptoms that seem to point 

 to a considerable participation of the central nervous system in the mechan- 

 ism of injury. 



The fifth dose range is marked by a process of damage that takes place 

 rapidly (instantaneous death). The mechanism of these effects proceeds 



7^ day 



7day 

 10\ 



Figure 1. Dose mortality curve of white 

 mice after whole body roentgen-irradiation. 



o o Curve obtained in 1943. • • 



Curve obtained in 1953. 



f\ 



Wm\n. 



/min. 



Lo^ doses 



probably from the destruction of a relatively large quantity of practically all 

 basic substances of the organism (molecular death). We shall see subse- 

 quently that probably each of these ranges really includes several mechanisms 

 of injury. This can be said definitely of the first and second dose ranges. 

 It was possible to demonstrate that the second dose range includes at least 

 three mechanisms which are probably connected with each other. 



Single doses, as small as lOOr to 200 r, already lead to a premature death 

 of the animals. Especially remarkable is the occurrence of a dose range, 

 varying slightly with the species and resistance of the animals, at least from 

 l,200r to 1 5,000 r. The mean survival time for white mice amounts to 

 3 • 5 days and is independent of the applied dose. This horizontal part of the 



82 



