_ (7 - 9 days). — -6- . . _ fc The platelet count may reach very low levels after two weeks, Ex- This group repre- ternal evidence of bleeding may occur within two to four weeks. In this group sents the lethal dose range in the classical pharmacologic sense, the symptom free period (the latent period) lasts from one to three weeks with little clinical evidence of injuries other than slight fatigue. At the termination of the latent period, the patient may develop purpura,* epiletion oral and cutaneous The mortality will be lesions, infections of wounds or burns, diarr!:ea or melena**, sipnificant., ith therapy the survival tine can be expected to be prolonged and if sufficient time is provided for bone marrow regeneration the survival rate will be increased, In group 1 (Survival impossible) and group 2 (Survival possible) the blood picture is not as well documented as in ercup 3 (Survival probable). There are ‘good clinical reasons to believe that in the lethal range the granulocyte depressions will be marked and below 1,000 per mm during the second week, in Jepan confirm this contention, Cbservat'’ons made However in the sublethal range it takes much longer for the granulocyte and platelet count of man to r each minimal values, as compared to other mammals, Despite the chaotic conditions that existed in Hiroshima the data of Kikuchi and Wakisaka (11) shows that there was a more rapid and marked decrease in groups 1 (Survival improteble) and group 2 (Survival possible) than in grcup 3 (Survival probable). Before going on to group 3 survival probable, I cannot | refrain from a comment on therapy. Much has beén learned from the experimental therapy of radiation injury in | animals, It has been conclusively sown thet protection can be afforded by the transplantation of bone marrow from one strain of animal to another, The protection afforded by transplantation of genetically specific material, that is from one member of the same strain to an ‘rradiated menber of the same strain, is very good ard long lasting. If the material for transplentation has its source in another strain of mouse, the protection is less marked and not as long lasting. * Blesding into sl:in ** Black stools from digested tlood | If the ROE ARcHyrs | 3h