Discussion 



89 



that are enzootic in the particular populations (such as pneumonia 

 in the rat, various kinds of enteric infections in the mouse) have a 

 lower incidence in the irradiated populations than in the controls. 

 What one sees then is a much more nearly rectangular life-table (less 

 mortality in early and middle life) with no actual increase in the 

 maximum span. L. D. Carlson, W. J. Scheyer and B. H. Jackson 

 (1957. Radiat. Res, 7, 190) at the University of Washington, Seattle, 

 found evidence of this sort, as did E. Lorenz and co-workers (1954. 

 In Biological Effects of External X and Gamma Radiation, ed. 

 Zirkle, R. E, p. 24. New York: McGraw-Hill). They irradiated rats 

 and mice, respectively, with small daily doses of gamma rays. We 

 have obtained similar results at Argonne Laboratory (unpublished). 



