RADIATION INJURY AND LETHALITY 



447 



0.1 



0.01 



0.001 



0.0001 



0.00001 = 



0.000001 



• Control 



© 5 r/day, duration of life 



<> 800 r in 54 days 



o 5 r/day, duration 

 of life, superimposed 

 on 800 r in 54 days 



100 200 300 400 500 600 



Time after beginning of treatment, days 



700 



Fig. 1. Gompertz diagram (logarithm of rate of mortality vs. time) for all causes of 

 death except lymphoma. Carworth female mice. Exposure begun at 90 days of age. 

 Note that, after a dose of 800 r delivered early in life, the Gompertzian is displaced 

 upward in about 200 days and thereafter runs parallel to the control line, whereas the 

 Gompertzian line for the 5-r/day group diverges progressively from the control Une 

 (the falling off in the last 100 days of each curve is due to a small percentage of mice 

 and is tentatively attributed to selection). These patterns have been verified in 

 several studies (42). The two trends intersect at an accumulated daily dose of about 

 1750 r, as against the theoretical value of 800 r for the rectangular assumption made 

 here. The discrepancy is due to deviations from the simple rectangular hypothesis 

 and to non-linearity in the relation between dosage and displacement of the Gompertz 

 function for massive dosages. The upper curve (open circles) is described more fully 



in the legend of Fig. 2. 



