68 Hematological T. KUMATORI subjects, i.e. Hiroshima cases, Marshallese, and cases exposed by reactor ac- ~ cidents (HEMPELMaNet al., 1952 ; AMANo, 1953 ; Cronkite et al., 1956 ; HasTEeRLix and Marineu, 1956; Gusxova and BatsocoLov, 1956; Anprews et al., 1961; JammeT, 1961), it is noted that all these cases similarly revealed the minimal value at about one month after exposure. 5. Bone Marrow The bone marrow was aplastic at the critical stage in severe cases, which showed remaining and proliferation of plasma cells and reticulum cells. Figure 3 shows the bone marrowof one of the severe cases. Comparing with normal 2g Bk at With the begin- ning of recovery, aplastic marrow changed to hypoplastic and then turned into a type of maturation arrest. ae In some cases, recovery was not complete even after one year. In less severe cases, the bone marrow was not aplastic but hypoplastic or in a type of maturation arrest even at the critical stage. Morphological and Functional Changes ; Several morphological abnormalities were observed: nuclear debris of lymphocytes, binucleated lymphocytes, vacuoles of neutrophils, toxic granulations of neutrophils, degenerative changes of blood cells, mitotic abnormalities of erythroblasts, ete. Motility and phagocytosis of neutrophils decreased remarkably. After one year, in some cases these functions were still lower than in normal persons. * ewe Red. 8 ow tlhe Bone marrow of one of severe cases at 5th week. bone marrow a lack of bone marrow cells was observed. 6. B tT =~ set, FOLLOW-UP STUDIES As above mentioned 16 to 18 fishermen have been examined on an annual basis. Figure 4 shows the changes of the cumulative distribution curves of leukocytes. The curve of critical stage appeared displaced far to the left of the normal curve, and gradually approached normal values. However, the curve of the 6th year was still displaced slightly to the left Tk eae oe Fig. 3 of ()) (cumulative). J ples sppiat b cn +P Peallgonveehdns? oe3 aa » Fig. 4 Leukocy tes +>. 3 Changes it eyes. neutrophils of normal Jap: the curve apt in the cumule However, the changes ° are represent A small 1 of erythrobl: 10 years. Cytoget results are § 1. The