1052 



RADIATION BIOLOGY 



exposure was begun and remained fairly constant at this level for the 

 first 100 weeks. No significant effect on erythrocyte and hemoglobin 

 values was observed in any of the exposure groups. 



Observations on Guinea Pigs. As is indicated in Table 16-4, the expo- 

 sure levels for this species were the same as for mice and rabbits. Within 

 a few weeks after the beginning of exposure a decrease in the leukocyte 

 values of the peripheral blood occurred in both males and females of the 

 five experimental groups, and the depression persisted throughout the 

 experiment (Fig. 16-12). The leukocyte depression was significant 

 (P 5i 0.05) even in the group exposed to 0.11 r. The degree of 



Table 16-4. Survival of Hybrid Guinea Pigs Exposed to Gamma Radiation- 

 Daily (8 Hours) 



° Acute exposure groups included. 

 6 Exposed for 31 days. 

 c Exposed for 61 days. 



leukocyte depression was correspondingly greater with the higher daily 

 exposure. 



The reduction in the leukocyte values of the various experimental 

 groups was caused by a decrease in lymphocytes in the 0.11- and 1.1-r 

 groups. In the 2.2-, 4.4-, and 8.8-r groups it was caused in part by a 

 decrease in lymphocytes but was largely a result of the more significant 

 reduction in heterophils. In fact, the characteristic terminal blood 

 picture is one of profound neutropenia, the proportion of heterophils 

 often being as low as 1-5 per cent. No significant alteration in the 

 eosinophil or monocyte values was observed in these experiments. In 

 general, there were likewise no significant morphologic changes in the 

 leukocytes in any of these exposure groups. 



No anemia of significance was produced in male or female guinea pigs 

 exposed chronically to 0.11 and 1.1 r. The male guinea pigs exposed to 



