4. Reticulocytosis (reticulocytes above 2 per cent). 5. Usythrocytosis (ROC over 5.6 million per c.rma. or hemoglobin over 13.0 52./103 cc. blood). Wilidams has anlyzed the value of biood studics and protection against radiag tion injury and has concluded that numcsous routine counts are unnecessary where good control of all circumstonces is maointaincd. Nowever, in radiation areas, more hishly controlled henatolosic studics arc needed in order to obtain more information on the threshold and pesmissabie values. Kolde cnd Wahlbers have analysed the lowering of the Lcubkecyte count in human beinss produced by minute amounts of whole-body radiation. They have utilised a statistical analysis. Al- though the mean Iecurocyte count 35 unchanged, the dispersion around the mean is considerably deczcased by low exposure to izvadictien, thus making it possible to use this statistical paranctes as on indicatica of izrzadiatica moosure. A complicating obsorvatieon is that of Wald ct al. who bas observed in the control populaticn in Japan that was not exposed to cadiation of the atomic bonbs that there has been a procressive decrease in the Leukocyte count over a period of the dest ten years. The scasons for this change ase obscure but obviously con= plicate the analysis of chronically exsesed popuiations. 8.230 Evaluation of Diced Chances. The above criteria cesult fron cithor a depression of of on inereased lability of hematopoiesis. The estebiishzuent of the presence of these criteria con be sscatly assisted by performing paraiiel studies on comparable groups o vumaa beings who ace tmown not to bo ettposed to radiation or any other toxic asent. Statistical comparison of the potentintiy exposed control group will heip to deter- ca. counts of the suspected srcup counts. In a similar manner the or incivicual con bea compared to the post-es:posure If there is a sicnificent chance in the Aattes, one can state with some certsinty that there kas been emcessive omposure to some tomic agent. soo 111d pre-e:posure A good

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