2,500 2,000 2 ° e ee ® e 3 1,500 = ® 2 e = ; e c-) j 1,000 F e e ° e e e e e 300 e Dose of Ist Oay 70 130 190 250 310 370 430 R Too 200 300 400 500 600 700 R Dose during 2 Weeks Fig. 3. stage in severe cases. which showed remaining and proliferation of plasma cells and reticulum 3 critical stoge cells. 8 a ~ w oa es ee . ‘ Cumutotive Persent a & 1 Correlation between Minimal Neutrophils Count and Dose of Gamma Radiation With the beginning of recovery, aplastic marrow changed to hypoplastic and then turned into a type of maturation arrest. Recovery was not complete even after one year. In the cases 8.8 not so severe as these, the bone marrow was not aplastic but hypoplastic or a type of matura\ ey ‘ tion arrest even at the critical stage. 6 xO RBC Fig, 4. eo Cumulative Distribution Curves (RBC) Platelets Platelets counts showed increasing depression, reaching minimum at the 4th-7th weeks. The recovery began during the following several weeks, The cumulative percentage curve still displaced to the lett of normal curve after one year, The results of other tests related to haemorrhave showed depression at the early stage in general and recovered by the l0ch week, Bone marrow The bone marrow was aplastic at the critical Morphological abnormalities Several morphological abnormalities, e.g. abnormal granules in lymphocytes or neutrophils, vacuoles in various leucocytes and megakaryocytes, giant nuclei and hyper-segmentation of neutrophils, binucleated lymphocytes, abnormal mitosis of erythroblasts, etc. were observed for about one year, especially at the critical and the recovering stages. Erythrocyte sedimentation rate was accelerated in the early stage in some cases. 4. Spermatopoiesis The examinations of spermatopoiesis were performed on 18 patients several times. Number of spermatozoa decreased about 2 months after the initial exposure, and azoo-