HEMATOLOGIC EFFECTS OF RADIATION 1063 



others were difficult to distinguish from monocytes. During the peak 

 of lymphocyte destruction, phagocytic monocytes with engulfed nuclear 

 debris were found in the peripheral-blood smears. Similar changes were 

 described by Henshaw et al. (1946) in mice following large single lethal 

 doses of 7 rays. 



During the phase of rapid reduction of granulocyte values in rabbits, 

 abnormal forms of this series were seen in the peripheral blood. These 

 cells showed nuclear deformity and disintegration to the extent that it 

 was impossible to determine at which stage of maturity the cells were 

 damaged (Jacobson and Marks, 1947; Jacobson et al., 1947; and Jacob- 

 son, Marks, and Lorenz, 1949). The nuclear membrane was destroyed, 

 and in most, instances, bluish nonspecific granules of uneven contour 

 filled the entire cell, covering the nucleus and cytoplasm to such an 

 extent that it was impossible to identify the cell other than to say it was 

 a damaged or degenerating leukocyte. Other bizarre forms were also 

 seen that were difficult to describe and impossible to categorize. The 

 cytoplasm of the heterophil may undergo changes following irradiation. 

 Occasionally it contained vacuoles and had a mottled appearance. In 

 some instances the granules of the heterophils appeared to be damaged 

 since cells were found in which some granules clung to the nuclear mem- 

 brane while the remainder of the cytoplasm remained clear. Another 

 type of cell seen in rabbits was one that resembled a basket cell but dif- 

 fered from it in having one or two distinct chromatin masses that were 

 deep blue against a network of destroyed perichromatin and cytoplasmic 

 disintegration. 



Atypical eosinophils characterized by irregularity in the granules, 

 both with regard to size and shape, were occasionally seen in the blood 

 smears of dogs following LD 5 o or higher doses of total-body roentgen 

 irradiation. Giant polymorphonuclear leukocytes were frequently seen 

 which appeared swollen and contained multilobed nuclei spread over the 

 cytoplasm-like globules, having an extremely fine filament branching 

 into eight or more lobes. 



DIRECT VERSUS INDIRECT EFFECT OF IRRADIATION 

 ON BLOOD FORMATION 



Lawrence, Valentine, and Dowdy (1948) reviewed the problem of 

 indirect effects and concluded that the hematologic or histologic evidence 

 for indirect effects of irradiation on nonirradiated blood-forming tissue 

 was unconvincing. Jacobson et al. (1949, 1950) found no suppression 

 of lymphopoiesis in the lead-shielded appendixes of rabbits given 800 r 

 of total-body X irradiation. Exposure of rabbits to this dose with shield- 

 ing of only a single Peyer's patch of the intestine did not appear to 

 inhibit or destroy the lymphocytes in the patch (Jacobson et al., 1952). 

 It must be borne in mind that dosages above the LD 5 o may produce 



