180 



NEUTRON EFFECTS ON ANIMALS 



tion, the females were killed and examined for the presence of fetuses. The 

 first 6 tests were made using the same 10 male rats (Group I). Group II, 

 consisting of 3 males, was used for the next 3 tests, and Group III, con- 

 sisting of 2 males, was used for the 10th test. Prior to the first test of 

 Group IV, given 113 n, one of the 10 rats in the group died. After the first 

 test another died. Subsequent tests were made with the remaining 8 

 animals. 



TABLE II 



Effect of 564 n and 113 n on Fertility of Male Rats 



11.3 n failed to destroy at any time the reproductive ability of the male 

 rats, the last test being made 225 days post-irradiation. 



When irradiated with 56.4 n (Table II) 10 to 20 per cent, of the males 

 were infertile between the 9th and 38th days. Between the 50th and 68th 

 days 100 per cent, of the males were infertile. Between the 68th and 143rd 

 days no tests were made. After the 143rd day some of the males w^ere 

 fertile. The time of maximum infertility of the rats appeared somewhat 

 later than the maximum histological injury. 



113 n affected fertility more (luickly than did 56.4 n. There was a 

 marked reduction in the number of fertile animals in 14 days, and infertility 

 in nearly all of them in 21 to 28 days. 



