PHYSIOLOGY OF RADIATION INJURY 961 



blood (Murray et al., 1948). Hemolysis has been seen in blood sub- 

 jected to heavy X irradiation (Ting and Zirkle, 1940; Liechti and Wil- 

 brandt, 1941; Frankenthal and Back, 1944; Halberstaedter and Leibo- 

 vvitz, 1947). Erythrocytes irradiated in vitro with polonium a particles 

 first shrink and then swell before hemolysis; these changes require large 

 dosages (5 X 10 5 rep) (Buchsbaum and Zirkle, 1949). Osmotic and 

 mechanical fragility of canine erythrocytes is apparently unaltered fol- 

 lowing exposure in vivo to X rays or neutrons (Davis et al., 1949; Ross 

 and Ely, 1947), but the thermal fragility of rat erythrocytes is reported 

 to increase during the first few hours after exposure of the whole animal 

 to 500 to 600 r (Goldschmidt et al., 1951). It is not known whether this 

 represents a direct effect of X rays on the red cell. 



That radiation anemia may be due, in part, to a hemolytic reaction is 

 suggested by the rapid decline of red blood cells, which is in excess of that 

 resulting solely from the absence of erythrogenesis, the active phago- 

 cytosis of erythrocytes, and the increased excretion of bile pigments 

 (Davis et al., 1949; Schwartz et al., 1947; Prosser, Painter, Lisco, et al., 

 1947). These facts do not in any sense constitute definite proof of a 

 direct action of radiation on the mature erythrocyte. The early anemia 

 may be partially explained by the loss of red cells from the circulation, by 

 the increase in plasma volume, and, to some extent, by the failure of 

 replacement. Large numbers of erythrocytes have been shown to appear 

 in the lymph within several days after irradiation, and extensive erythro- 

 phagocytosis and hemosiderosis have been seen in the lymph sinuses of 

 irradiated animals (Furth, Andrews, et al., 1951). Destruction of 

 erythrocytes may also be accomplished by the toxic materials that are 

 liberated from damaged tissues or from infectious organisms. While 

 increased excretion of bile pigments is suggestive of red cell destruction, 

 this may also be attributed to cessation of red cell production or to some 

 aberration in the incorporation of hemoglobin into young erythroid cells. 



Although each of the ionizing radiations affects the hematopoietic 

 organs in the same qualitative manner, their relative effectiveness varies 

 (Lawrence and Lawrence, 1936; Jacobson and Marks, 1946). The 

 X-ray-to-neutron ratio for the acute lymphocyte and granulocyte 

 response in rabbits is around 6.0 (Jacobson and Marks, 1946). Only 

 minimal blood changes are seen after external irradiation with /3 rays 

 (Raper and Barnes, 1951a). This is consistent with the localization of 

 radiation effects. Granulocytes may increase several weeks after external 

 /3-ray exposure of rabbits, but it is noteworthy that granulocytosis 

 coincides with infection of the ulcerated skin. On the other hand, exten- 

 sive damage to the hematopoietic tissues and concomitant changes in 

 peripheral blood have been observed following poisoning with internal 

 emitters (Bloom and Jacobson, 1948; Jacobson, Marks, and Lorenz, 

 1949). Differences in the hematologic effects seen after administration 



