NEUTRON EFFECTS ON ANIMALS 149 



subject were made by 1) a comparison of the mortality response of older 

 and heavier rats (Group Xa) with that of younger and smaller ones (Group 

 Xb); 2) a comparison of the mortality response of rats, small because of 

 dietary restriction (Group XIa) with that of larger rats of the same age 

 whose diet had not been restricted but supplemented (Group Xlb); 3) a 

 comparison of the mortality response of rats of a given weight (Group Xlb) 

 with the response of rats of the same weight, but older (Group XIc); 4) a 

 comparison of the mortality response of small young rats (Group Xlla) 

 ^^^th that of older and larger ones (Group Xllb), both fasted for 

 3 days immediately prior to irradiation. All rats had free access to water. 



The rats were irradiated (Enns et al. (1)) in Box No. 7 with 141.0 n at the 

 approximate rate of 1 n/min. 



Small young rats were found to be more radiosensitive than were older 

 and heavier rats (Table I). Rats of the same age, but differing in weight 

 because of dietary restrictions, were found to differ in their sensitivity, the 

 smaller rats being the more sensitive. Rats of the same weight, but differ- 

 ing in age, appeared, on the basis of the limited data, to differ in sensitivity, 

 the younger ones being the more sensitive. 



The total mortality was the same for rats of different ages and weights 

 fasted prior to irradiation, but the younger and smaller rats apparently 

 were more sensitive to irradiation than the older and larger ones because 

 they died sooner after irradiation. 



The gross clinical changes in the smaller and younger rats after neutron 

 radiation were more pronounced than in the older and heavier animals. 

 In all rats after irradiation, the hair had a dry, coarse, rough appearance. 

 All of the young small rats were smeared and dirty. They were reluctant 

 to move and did so sluggishly, stiffly and ^nth arched back. They were 

 markedly dehydrated and gaunt in appearance, which reflected the greater 

 relative reduction in food intake of the j'ounger, smaller rats than of the 

 older, heavier animals. 



These results suggest the advisability, ^^■hen comparing radiation effects 

 on animals, of taking into account the variable factors of size, age, and 

 nutritional condition. 



LACK OF INFLUENCE OF VITAMIN E ON RECOVERY OF TESTES FROM NEUTRON 



IRRADIATION INJURY 



The food intake of rats receiving 56.4 n has been shown to l)e consider- 

 ably reduced, thus reducing the amount of vitamins available to the ani- 

 mals. Testicular injury found in rats after neutron irradiation (3) may 

 have been due, to some extent, to lack of vitamin E, or to disturbances 

 in the absorption and utilization of vitamin E. 



Four groups of 5 male rats were used: one group, XIV, was fed vitamin 



