156 



NEUTRON EFFECTS ON ANIMALS 



Two additional groups of rats received 113 n: one group received it in 

 one dose, the other received 56.4 n on each of 2 successive days. 



The changes in the total white blood cell and absolute lymphocyte counts 

 were found to be approximately the same, whether single or divided doses 

 were administered (Table I). 



Neutron Dose and the Degree of Depression. Five groups of rats, each rat 

 weighing appi'oximately 200 gi-ams, were given 11.3, 28.2, 56.4, 84.6 and 

 113 n respectively. Each group consisted of 20 rats, with the exception 

 of the group receiving 84.6 n, which had 10 rats. Blood counts were made 

 daily until definite signs of recovery appeared. 



With all doses of neutron radiation given, the decrease in numbers of 

 cells began in the first 24 hours. As the dose was increased the initial 

 decrease became greater. The greatest depression in the number of leuko- 

 cytes and absolute number of neutrophils occurred at different intervals 

 after irradiation, while the lowest number of lymphocytes always occurred 

 on the 2nd day. The period of time for return to the pre-irradiation blood 



100 



Fig 

 count, 

 count; 



II. 3N 



28.2 N 



56.4 N 



64.6 Kl 



II3N 



DOSE 



2. Lowest white blood cell count, expressed as per cent, of pre-irradiation 

 at different dosage levels. # Absolute lymphocyte count; O Total leukocyte 

 A Absolute neutrophil count. 



values was found to vary with the dose. The greater the dose, the greater 

 was the depression and the longer the duration of the depression. 



The lowest number of leukocytes occurred on the 7th, 4th, and 2nd days 

 for 11.3 n, 56.4 n and 113 n respectively while the lowest absolute number of 



