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UPTON, CONKLIN, MCDONALD, AND CHRISTENBERRY 



0-10 -0-12 mg/mouse, dissolved in 1 mg/ml physiological saline solution. 

 The doses of each agent were selected, on the basis of earlier pilot experiments, 

 to approximate the LDgo/SO. After treatment, the mice surviving thirty days 



Table I. Late somatic effects of HN2, TEM, and X-rays 



Agent 



30-day survival 

 Treated 

 total ( %) 



Mean age Incidence of neoplasm (%)t 



at deathf Leukaemia Tumour 



(days) Myeloid Thymic Lung Ovary 



f Based on thirty-day survivors only. 



were housed 8 to 10 per cage and observed until death. Some animals in each 

 treatment group were examined periodically with the split-lamp for lens 

 opacities, according to methods described earlier (Upton et al., 1960). After 

 death, every mouse was necropsied, and histological studies were carried out, 

 as necessary, for diagnosis. 



RESULTS 



All three agents shortened the life-span (Fig. 1), the effect being largest 

 for X-rays and smallest for HN2. The life-shortening effects were equally 



100- 



80 



60- 



40- 



20- 



100 200 300 400 500 600 700 800 900 1024 

 Age (days) 



Fig. 1. Longevity of thirty- day survivors, with and without neoplasms, in relation to time 

 after treatment. D, X-rays; A, TEM; •, HN2; O, controls. 



evident, moreover, in mice free of neoplastic disease (Fig. 2), although the 

 incidence of certain types of neoplasms was greatly increased (Table I). The 

 tumorigenic effects of the agents differed fom one organ to another, no 



