34 NEUTRON EFFECTS ON ANIMALS 



ation of the structure of this organ. Kidney, ovary and Hver were also 

 infiltrated by undifferentiated tumor cells although the liver showed some 

 evidence of regeneration. The tumor seemed to have cytolytic properties 

 since many of the liver cells appeared to be eaten away by the adjacent 

 tumor cells. 



The two female rats sacrificed on the 244th day at the termination of the 

 experiment were grossly normal except for enlarged and hemorrhagic 

 adrenals and hemorrhagic ovaries. Microscopically, both showed marked 

 edema of the deeper cortical portion of the adrenal and the spleens were 

 contracted with little blood in the sinuses. Splenic follicles were small 

 and inactive and there were numerous neutrophils present and also small 

 areas of hematopoiesis. 



One of these rats showed a bilobular tumor, 2x1x1 cm., first noted 

 on the 200th day, which was cut with difficulty, was capsulated and ap- 

 peared granular in structure. Microscopically, this tumor was identified 

 as an adenocarcinoma probably of mammary origin. 



Since non-irradiated rats did not show any of the gross or microscopic 

 pathologic changes described above, the changes observed in the irradiated 

 animals probably were caused by neutrons. The available autopsy data 

 suggest that atrophy of lymphoid tissue together with degeneration in the 

 spleen are the primary changes produced by neutrons. The importance 

 and significance of the presence of tumors in some of these rats will be 

 considered later with comparable findings following repeated doses of 1.8 n 

 of neutrons. 



Neutron Doses of 1.8 n Repeated. Three different groups of rats were 

 exposed to repeated doses of 1.8 n, as follows: 



1. Twelve female rats received 1.8-n doses of neutrons, six days a week, 

 for a total of 251 doses in 299 days (an accumulated neutron dose of 452 n) 

 and were kept under observation for a total of 330 days. 



2. Six female rats were irradiated as for the first group l)ut for only 

 172 doses in 203 days (accimiulated neutron dose of 310 n). These rats 

 plus four additional non-irradiated animals were kept under observation 

 for only 248 days. 



3. Six male rats were irradiated as for the second group and together 

 with four additional non-irradiated animals were kept under observation 

 for only 247 days. 



In theee three experiments, repeated hematological checks showed that 

 there were no significant differences between the irradiated and non- 

 irradiated animals, — all values for total leukocyte count, differential leuko- 

 cyte count, erythrocyte count and blood hemoglobin levels being within 

 normal limits. Only the rate of growth as indicated by the changes in 

 body weight showed any significant variation between irradiated and non- 



