of the total white blood count (Coetfierent Ob Correbition af O.9}. Thus the, Hhucttattcrs aa tata count were due Co changes inthe neatrophile count. ‘This: wits ¢rue of both the alder and younwer are pregps. Tecan be seen trom ‘Fable 4.2 that the nealrophile count was cousistentiy prealer than the lymphocyte count in fhe older age group, In the younger groups, differences ta the neu trophole and lympbocyte coffit were tess marked and on six occasions the lymphoevie count wats greater than the neutrophile count, Platelets were first counted 10 days affer exposure, at which time platelet values of the older ape proups were approximately 70 per cent of the control group (Fig. 4.4). Followane thas, the platelet count fell reaching a low of approximately 35 per cent of control value during the fourth week. The platelet count rose during the 5th week and reached the value noted for the initial counts on the 10th day. A second decrease in the platelet count (P< 0.01) developed dur mg the 7th and 8th weeks, and values remained at approximately 70 per cent of the control group during the remainder of the observation period. The pattern of platelet counts in the below 15-year group was remarkably similar to that noted in the older aye groups, Differences between the age groups were less apparent if the platelet counts were expressed as per cent of Is the control group. 4.6 ALLINGINAE GROUP In this proap there were only three yndividuals below age 5. For this reason, remarks will be confined cssentiatly ta the older age group. The absolute neutrophile count fluctuated around the control value for the first six weeks of observation (Table 4.3}, At this time the counts began to fall, and a value approximately 75 per cent of the control count was reached and maintained throughout the duration of the obser- vation period. The lymphocytes in this group fell to a value of 55 per cent of normal during the first week. The counts then fluctuated around this value throughout the period of observatic a, and no definite upward trend of the lymphocyte count was noted during the period of observation. aa As was noted in the Rongelap group the lymphocyte counts remained at an essentially constant low level throughout the period of observation. The total|leukocyte eount in this group also reflected changesin the neutrophile count. The platelet counts in the Ailinginae group were low, approximately 75 per cent of normal, when first enumerated on post-exposure day 10, The counts remained at this level during the second and third week; however, a definite fal] in count was noted during the fourth week when a low value 45 per cent of control was attained. The counts returned during the fifth week toa value approximately 70 per cent of the control level, where they remained for the duration of the observation period. A secondary fall, as observed in the Rongelap group was not detected. 4.7 , i ee “i UTIRIK GROUP In the greater than 5 age groupthe total white blood cell and neutrophile counts were depressed slightly below control values during the first and second weeks (Table 4.4). The lymphocyte counts were below control levels consistently, and the total white count equal to the control value obtained on day 29 was due to a neutrophilic leukocytosis. Platelet counts on the 29th day were significantly lower than on the 19th day and were lower than control values. The 29th day coincides with the time of maximum depression for the more heavily exposed groups. 4.8 RONGERIK GROUP (AMERICANS) The neutrophile count in general reflected the time course of the total leukocyte count (Fig. 4.5), Neutrophiles accounted almost entirely for the marked rise in total count on postexposure day one, and the values for absolute neutrophile count fluctuated near the control ‘ woes 80