HISTOLOGICAL CHANGES AFTER IRRADIATION 1137 



(Halberstaedter and Ickowicz, 1947). Adrenal hypertrophy and fatty 

 infiltration of the liver, not reported by careful observers after direct 

 irradiation of either the adrenals or liver, are observed as a secondary 

 toxic effect of roentgen rays (Leblond and Segal, 1942). 



The importance of the spleen (and other lymphatic organs) in radiation 

 injury is emphasized by experiments in which the LD 50 for mice was found 

 to be nearly twice as great when the spleen was protected with lead during 

 total-body irradiation as when it was not (Jacobson et al., 1949). 

 Such protection of the spleen during irradiation of the rest of the body 

 not only lengthens the survival time of these mice, but also lessens 

 the injury to their irradiated lymphatic tissues and bone marrow; these 

 show greater powers of regeneration than when the whole body is 

 irradiated (Jacobson et al, 1950)— further evidence of the fact that, 

 whereas the hematopoietic process is very radiosensitive, the hemato- 

 poietic organs are potentially radioresistant. 



REFERENCES 



(Information regarding availability of government reports indicated by an asterisk 

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