448 



RADIATION INJURY AND LETHALITY 



1.00 



2.00 



3.00 - 



o 



4.00 



5.00 



700 



100 200 300 400 500 600 



Time after beginning of treatment, days 



Fig. 2. The summability of radiation lethality when expressed in units of the 

 Gompertz function. The open circles were experimental values obtained from a 

 single group of mice which received a fractionated dose of 800 r delivered in 54 days, 

 and also a daily exposure of 5 r/day for the remainder of life, both patterns beginning 

 at 90 days of age. The half-filled circles were obtained by summing the following 

 Gompertzian components from three separate groups of mice (see Fig. 1 ) : 



1. The component in excess of control for a group which received 800 r in 54 days. 



2. The component in excess of control for a group which received 5 r/day for dura- 

 tion of Ufe. 



3. The Gompertzian curve of the control group. 



There is good agreement except for a slight deficit of the summation from the ex- 

 perimental values in the first 200 days. 



