32 NEUTRON EFFECTS ON ANIxMALS 



cyte count did not reach as low values (see Fig. 1). In addition, these 

 animals did not appear ill during the period of observation and were grossly 

 normal at autopsy except for some atrophy of thymus and testes. 



After a dose of 120 n of neutrons, all of the six male rats died in from 

 7 to 24 days. The observations made on these animals were practically 

 the same as those described above for the 3 deaths in the 60-n group. 



In the 180-n and 240-n groups, all animals died within 6 to 8 days. 

 These rats showed a continuous and severe loss in weight, complete loss of 

 appetite after the first 60-n dose, and a leukocyte count which approached 

 zero the day prior to death. Furthermore, there was an acute diarrhea 

 and on autopsy the primary finding was that of severe emaciation. In 

 addition, the stomach was usually found to contain considerable undigested 

 or partialh' digested food while the intestinal tract was devoid of any 

 traces of food. Considerable yellowish mucoid material, frequently blood- 

 stained, was present in the intestinal tract. 



Neutron Dose of 10 n Repeated Twelve Times. In this group, 6 male and 

 5 female rats were irradiated at the same time and received 10-n doses of 

 neutrons during the first fourteen days of the experiment with no irradia- 

 tion on the third and fourth days. The observed mortalities, changes in 

 weight, total leukocyte counts, differential leukocyte counts, erythrocyte 

 counts and blood hemoglobin levels were averaged for all eleven animals 

 and are graphically summarized in Fig. 2. 



It should be noted that all males died in from 24 to 60 days after a con- 

 tinuous loss in weight until time of death when the average weight loss 

 was 29.1 per cent of the initial weight. Prior to death the leukocyte 

 counts, erythrocyte counts and blood hemoglobin levels had passed through 

 a minimum, had increased, but had not yet reached the initial levels. 

 Five of these rats died during the night and post-mortem changes were so 

 far advanced at autopsy that significant data and tissues for histological 

 study could not be obtained. The single remaining animal of this sex was 

 sacrificed on the 60th day when comatose and gave a gross picture of severe 

 emaciation with slight indications of atrophy of lymphoid tissues and of 

 the testes. 



On the other hand, only three of the five female rats of this group died 

 on the 43rd, 156th, and 174th day, respectively. These deaths occurred 

 at a time when the weight and hematological values had at least increased 

 above the minimal values and in the last two cases had reached or even 

 exceeded the initial values. Post-mortem changes were so far advanced 

 on autopsy of the two rats dying on the 43rd and 174th day that no sig- 

 nificant pathological data could be obtained. 



The rat dying on the 156tli day was actually sacrificed at that time 

 when it was comatose, showing severe emaciation and complete posterior 



