NEUTRON EFFECTS ON ANIMALS 181 



Discussion. The germinal epithelium is a tissue of such labile character 

 that it is readily affected by such diverse influences as heat (5), vitamin 

 deficiency (6), febrile condition, alcoholic intoxication, infectious diseases, 

 sexual stimulation and penetrating radiations. It seems probable, there- 

 fore, that the effect of neutron irradiation on the testicle is brought about 

 not only as a direct injury but also indirectly by the increase in body tem- 

 perature, the reduction in food consumption and impaired digestion (7), 

 and possibly an effect on other endocrine glands. In the animals reported 

 here the addition of vitamin E to the diet neither prevented nor ameliorated 

 the injury caused by neutron irradiation (7). Reduction in weight of the 

 testes apparently is due to atrophy of the seminiferous tubules. 



Spleen 



A. Changes in Weight. Eighteen groups of rats were used, 10 of which 

 (Table I, 1-10) were used in the studies on changes in weight of testes. 

 Group 14 served as a control for groups 15-21 which were given 56.4 n in 

 Box No. 7. At intervals after irradiation the rats were killed, the spleens 

 removed and weighed. Sections were then prepared and stained with 

 hematoxylin and eosin for microscopic examination. 



56.4 n. Changes in the wet weight of the spleen at intervals up to 14 

 days after irradiation are shown in Table I. A maximum loss in weight of 

 nearly 50 per cent, had occurred by the 4th day after irradiation. This 

 was followed by a rapid return to almost normal weight by the 10th day. 

 Dry weights of these spleens showed the same relative changes. 



Loss with subsequent increase in weight of the whole animal as well as 

 of the spleen occurred. The ratio of animal weight to spleen weight, how- 

 ever, increased, showing a relatively greater loss in weight of the spleen 

 than in weight of the whole animal. As the spleen weight returned to 

 normal, the ratio decreased to almost normal, groups 14-21, Table I. 



60, 120, 180, 2-W n. Groups 6-10, Table I. Initially the average 

 weights of the rats of these groups were approximately equal. After 

 irradiation there were marked reductions in weights of the animals and the 

 spleens except in Group 7 where the average spleen weight was not reduced. 

 It is probable that the longer observation period for this group allowed 

 nearly complete recovery of the spleen. 



The short observation periods and the relatively great effect on the 

 spleens of Groups 9 and 10 indicate the spleen is quickly affected by neu- 

 tron irradiation. 



17.5, 32.5, 47.5 and 62.5 n. Groups 1-5, Table I. There appeared to 

 be a slight reduction in the weight of the spleen in relation to animal weight 

 35 days after irradiation, but the differences were not great. It is obvious 



