1070 RADIATION BIOLOGY 



cells of the shielded tissue (Jacobson, Simmons, Bethard, et at., 1950; 

 Jacobson, Simmons, Marks, et at., 1950). 



The survival of mice exposed to 1025 r of total-body X irradiation is 

 approximately 30 per cent if part of the exteriorized liver (0.8 g), the 

 exteriorized intestine (2.5 g), the entire head (3.0 g), or one entire hind 

 leg up to the thigh (1.5 g) is lead shielded during exposure. Without 

 shielding, only 0.8 per cent survive this dose; with spleen shielding at 



I- 



o 



o 



20 



10 

 8 

 6 



4 

 3 



I 

 0.8 



0.6 



0.4 

 0.3 



0.2 



-3 3 6 9 12 15 



TIME AFTER X RAY, days 



19 



-•CONTROLS 0---0 OPERATED CONTROLS 



e ®600r WITH SPLEEN EXTERIORIZED 



AND DISTAL VESSEL CUT 



cr-— A 1300 r WITH SPLEEN SHIELDING 

 AND DISTAL VESSEL NOT CUT 



Fig. 16-20. Comparative effect of 600 r of total-body roentgen irradiation (spleen 

 exteriorized and distal vessel cut) and of 1300 r with lead shielding of the exteriorized 

 spleen (distal vessel not cut) on the leukocyte values of CF! female mice. 



least 76 per cent survive. Shielding one exteriorized kidney (average 

 weight 0. 19 g) does not enhance survival. Recovery of the hematopoietic 

 tissue, as judged by histopathologic and hematologic examination, is 

 under way by 8 days in liver- or intestine-shielded animals, whereas after 

 lead shielding of the head, recovery of these tissues is delayed even longer, 

 and recovery of hematopoietic tissue is nil with kidney shielding (Jacob- 

 son, Simmons, Marks, and Eldredge, 1951; Jacobson, Simmons, Marks, 

 Gaston, et al., 1951). 



The effect of spleen or appendix shielding on the survival of irradiated 

 rabbits has not been carefully studied, but it is clear that no enhancement 

 of survival occurs such as is observed in spleen-shielded mice or rats. 



