NEUTRON EFFECTS OX ANIMALS 



155 



reached its maximum depression at that time (Fig. ID). The blood 

 changes occurring after 11.3 n and 5(j.4 n differed in time and intensity only. 

 113 n: Immediately after irradiation there was an enormous drop in the 

 total leukocyte count (Fig. IE) which wa. lowest on the 2nd day. The 

 count had risen above the pre-irradiation level by the 28th day, and re- 

 turned to pre-irradiation values after the 40th day. The changes in the 

 differential values for the lymphocytes and neutrophils are shown in Fig. IF, 

 with a relative lymphopenia and neutrophilia indicated. Both the abso- 

 lute number of neutrophils and the absolute number of lymphocytes were 

 lowest on the 2nd day (Fig. IE). The lymphocyte count paralleled that 

 of the white blood cell count. 



TABLE I 



Effects of 56.4 n and 113 n, Given in Single and Divided Doses, on the White Blood 



Cells of Rats 



As the total leukocyte count approached pre-irradiation values, numerous 

 abnormal cells were found in the blood smears. Some of the lymphocytes 

 were very small, some showed cytoplasmic vacuolization. Neutrophils 

 containing 8 or more segments in the nucleus were seen along with oc- 

 casional degenerated forms. There were a few small vacuolated basket 

 forms. Abnormal unclassified cells which were present shortly before 

 recovery occurred twice as frequently in this group as in the group given 

 56.4 n, and 10 times as frequently as in non-irradiated rats. 



Eosinophils, basophils, monocytes, myelocytes, blast forms and plasma 

 cells were so few and variable in number that no conclusions could be 

 drawn concerning the effect of neutrons upon them. Besides the abnormal 

 cells, the total number of primitive cells increased after irradiation. 



Comparison of Effects of Single and of Divided Doses. One group of rats 

 was given 56.4 n in a single dose, the 2nd group was given 28.2 n on each 

 of 2 successive days, the 3rd group was given 11.3 n on each of 5 successive 

 days, the 4th group was given 5.6 n on each of 10 successive days. The 

 total dose was approximateh^ 56.4 n in each case. 



