With the exception of the development of shin lesions and epilation, physieab cago Gians at no time revealed findings in any group that could be attributed with certiuiuty to eadiation, The various clintcal conditions encountered in the most severely exposed groups were nol re - markably different from those seen in the least exposed Utirik group. ‘Phe skin destons and epilation appeared about the 12th to 14th post-exposure days. 2.3) CLINICAL OBSERVATION AND THERAPY AS RELATED TO HEMATOLOGICAL, FINDINGS _ Although detailed hematological findings are presented in chapter 4, certain considerations of the relation of clinical to hematological findings are discussed here. 2.3.1 Leukocyte Counts Between the 33rd and 43rd post-exposure days, LO per cent of the Rongelap tndividuadls reached an absolute yranudocyte level of L000 per cubie millimeter or below. ‘Phe lowest count observed durtag this pertod was 700 granulocytes, During this interval the advisability of piv ing prophyhicetic antibiotic therapy to such individuals was carefully reconsidered. However, prophylactic antibiotics were not instituted because of the following considerations; (1) AM individuals were under continuous medical observation so that infection would be discovered in its earliest stages. (2) Since some individuals might require antibiotics for long periods of time if infection occurred, the premature administration of such drugs would not only possibly obscure medical indication of treatment, but might potentially lead to the development of drug resistant organ- isms in an individual with an already lowered resistance to infection. (3) There is no accurate knowledge of the number of grarulocytes required by man to pre- vent the types of infection seen in agranulocytosis. (4) The observed situation was not strictly comparable to agranulocytosis with an aplastic marrow due to potentially lethal doses of radiation. In the latter instance, granulocytes fall rapidly and there are practically none in the circulation wher infection occurs. In the present group of individuals exposed to radiation, although most counts were approximately one-fourth of normal, the fall to that level was gradual and there was some evidence of granulocyte regen eration. White counts were repeated at three or four day intervals on all of the exposed individuals and more frequently on those with the lowest counts. Those with symptoms or elevated tem- peratures were treated only after an attempt to establish a diagnosis was made, even if a period of observation was necessary. During the observation period, the patients were examined at frequent intervals and the temperature checked every few hours. Twenty-seven individuals had total leukocyte counts of 4000 or below or absolute neutrophile counts of 2500 or less at some time during the period of observation. Of these 27, 13 had symptoms of disease that required evaluation for possible antibiotic therapy. Eleven of the 13 had severe upper respiratory infections, one individual had abdominal pains and fever, and one had urticaria (hives) with fever. The incidence and type of symptoms in the group with low leukocyte counts did not differ materially from those in the remainder of the population and it appeared that the occurrence of disease and the presence of leukopenia was coincidental. The 13 instances in which it was necessary to consider the use of antibiotic therapy in neutropenic individuals are summarized below: Eleven of the 13 individuals had severe upper respiratory infections. Eight of these had malaise, sore throat, nasal discharge, and temperatures that varied between 99 and 101.4°F and then feli to normal within a 12 hour period. Since the response of this group to upper respiratory infection appeared identical with that of individuals without neutropenia, no therapy was given. Two of the 11 had marked malaise, headache, abdominal pain, nausea, diarrhea, and high fever. Both were children, one age seven, the other age two. In both instances, the symptoms were out of proportion to the physical findings, which were negative except for head colds and mild pharyngeal injection. The seven-year old child had a temperature of 102.6 when first seen 25