118 



NEUTRON EFFECTS ON ANIMALS 



cell count increased to an abnormally high value and the rabbit rapidly 

 declined in health. 



Repeated doses were found to result in much lower white blood cell 

 counts than single doses, as shown in Table II. 



10 n/day doses. The effect on the white blood cell count of irradiation 

 ^\^th 10 n/day over an extended period is illustrated by the graph for 

 rabbit No. 29 in Fig. Id. As may be seen, this daily irradiation tended to 

 maintain the count at low values. During recovery the white cell count 

 was sometimes characterized by overcompensation followed by a final 

 return to a normal level. Ten other rabbits, also given a total of 290 n in 

 10 n/day doses, showed essentially the same response, except for a varying 

 survival period which ranged from 2 to 97 days after irradiation was com- 

 pleted. Some of the rabbits were irradiated ^\ith only one side exposed 



TABLE II 



Miuimum White Blood Cell Values Resulting from Repeated Doses of Xeutrons 





toward the source of irradiation while others were exposed on alternate 

 sides on alternate days : this did not alter the effect on the white cell count. 

 Preliminary studies with rabbits given 5 n/day gave quahtatively similar 

 results, although complete experiments under these conditions were not 

 made. 



The effect of neutron irradiation on the white blood cell count of rabbits 

 was found to resemble closely that on the white blood cell count of rats 

 and mice (2, 3) resulting from irradiation with neutrons or mth X-rays. 



Varialion in Body Weight with Irradiation. The general health of the 

 rabbits, as indicated by body weight, revealed their varying sensitivities 

 to neutron irradiation. Animals given large amounts of irradiation lost 

 considerable weight and showed diminished appetite. Rabbits exposed to 

 a dose of only 34 or 55 n exhibited rather uniform continuous growth as 



