-18- infrared heat lamp, 110 c/m after flaming and 4 c/m after covering with aluminum foil 4.7 mg/cm? in weight. of A total correction factor 112 was used (based on a secondary Fe° standard obtained from Dr. C. A. Finch, University of Washington) to convert to disintegrations per minute. The radioisotopes of zinc, cobalt and manganese were identified by their gamma energies and the disintegrations per minute were calculated from the gamma spectrum curves of the different fractions. Radiostrontium was not detected in the citrate fractions whereit would be expected to occur. Radiochemical precipitation determinations revealed the presence of small amounts of radiostrontium in the bone of fish collected at Kabelle Island. No radiostrontium was detected either in the liver or muscle of any of the fish taken at Ailinginae or Rongelap Atolls or in the bone of fish from Enibuk Island or Rongelap Island. Table 6 con- tains data on the Sr?9 contentin fish tissues collected during and since 1954 at Rongelap Atoll by this Laboratory. Except for traces of Sr90 in goatfish and reef fish bone from the Kabelle Island 1957 collections and in bonito bone from the 1955 collections at Labaredj, no radiostrontium has been detected in the fish tissues. A summary of the data on the radioisotopes obtained from the liver tissue sample of reef fish from Enibuk Island is contained in Table 7. In total radioactivity, Zn§5 contributed about 40 per cent, CoS? Cos, ” sf ‘nee yi abe