116 



NEUTRON EFFECTS ON ANIMALS 



variations are shown in Table I in which mean values of the counts and 

 corresponding standard deviations from the means are presented for each 

 of 15 different animals. 



Variation in White Blood Cell Count with Neutron Irradiation 



55 n/day doses. A typical change in white blood cell count after irradi- 

 ation was that shown by rabbit No. 22, given 55 n/day for 2 days; the 

 data are presented graphically in Fig. la. The day-to-day variability of 

 the normal count may be seen in the first part of the graph. After irradi- 

 ation, an immediate rapid diop in count occurred; the minimum value was 



TABLE I 



Normal White Blood Cell Counts of Rabbits 



reached in 3 days and was followed by a recovery period which lasted about 

 1 month. Finally, this extended recovery period was followed by a further 

 slight increase in count which, however, proceeded at a diminished rate. 

 Re-irradiation of recovered animals produced a repetition of the response, 

 as shown for rabbit No. 13 in Fig. lb. Other rabbits, given total irradiation 

 of 34-220 n over periods of 1-4 days, also exhibited a precipitous drop in 

 white blood cell count immediately after irradiation, and required approxi- 

 mately 1 month for the return of the count to normal. Some animals, 

 however, survived the irradiation for only a short time. This failure to 

 survive began at total irradiations of 165 n and above, given in 55 n/day 



