394 



INFLUENCE OF EXPOSURE FACTORS 



pathologic findings, several types of experiments have yielded results 

 which implicate the intestine and lymphoid organs in this "early death" 

 effect. Quastler (personal communication) has found that the effect of 

 whole-body exposure in this dose range (and above) can be duplicated 

 almost completely by irradiation of the intestine alone. The intestine 



0.1 



1 10 



Exposure, thousands of roentgens 



100 



Fig. 1. Diagram of effects of a wide range of exposures (whole-body, x-irradiation) 

 on survival time. "Late death": animals die only a few weeks before controls; 

 "early death" : survival, after irradiation, of only 1 month or less; "immediate death" : 

 survival of only 2-5 days after irradiation; "instantaneous death" : animals die during 

 or within a few minutes after massive high-intensity irradiation. Data based pri- 

 marily on experiments with mice (see text for references and discussion). 



was exposed through a surgical incision of the abdominal wall with the 

 rest of the body protected by lead shielding. Jacobson et al. (33, 34) 

 have irradiated mice with exposures from 600 r through 1200 r of total- 

 body irradiation with and without lead protection of the surgically 

 mobilized spleen. The dose required to kill half the animals with the 

 spleen protected is almost twice as great as the dose necessary to kill 

 half the mice with the spleen included in the irradiation. The develop- 

 ment of anemia is obviated, and the severity of the leukopenia, etc., is 

 significantly lessened in the spleen-protected animals. 



The next part of the curve, marked "immediate death," indicates that 



