RADIATION-INDUCED LIFE-SPAN SHORTENING IN MICE 



281 



might therefore be more correct to look upon radiation as bringing about a 

 new late somatic change which is quite absent in the unirradiated population. 

 Another characteristic pathological change occurring with advancing age 

 in several strains of mice, including ours, is to be found in tlie kidney. The 

 condition is described under several names in the literature, but for the CBA 



50 



25 



llOOr 



Control 



Limiting value obtained 



from previous studies 



in which animals were 



allowed to die 



9 12 15 



Age (months) 



Fig. 3. Incidence of lung tumours with increasing age in serially killed control and 

 X-irradiated CBA male mice. 



animals, the term papillonephritis, as defined by Dunn (1944), is thought to 

 be most applicable. The effect of the radiation treatment on the series of 

 developmental changes leading to papillonephritis, as seen in the control 

 mice, is different, yet again, from the other examples quoted above. From 6 

 months of age, when the first pathological changes become visible, the steady 



9 12 



Age (months) 



13 



21 



Fig. 4. Incidence of cataracts with increasing age in serially killed control and X- 

 irradiated CBA male mice. 



progression of the various stages of papillonephritis follows the same pattern 

 in both control and irradiated animals. Lesions, severe enough to be included 

 in the probable causes of death, begin to appear at 18 months of age. As the 

 serial killing has not gone beyond twenty months, the total number of cases 

 in this experiment is stiU very small. From previous experiments, 40% of 



