ai kt as ae I diccTh naeee Baeine Tar aia eT ea A : nae embed. a -7- Procedures Used in Collecting and Processing Samples and Recording Radioactivity The procedures used in collecting samples of biological material in the Marshall Islands have evolved over a period of years. An effort was made during each expedition to obtain as complete a sample as necessary for an adequate evaluation of the problems studied, without completely swamping the Laboratory with samples. To carry out the program of sampling, specific animals and plants with wide distribution have been selected for study. From these selected samples certain tissues are evaluated to determine the distribution of radioactivity. Collections made in the field were retained on ice or frozen until they | could be returned to the Division of Biology and Medicine field laboratory at Parry Island. There the organisms were identified, selected tissues were dissected, weighed and then dried. The packaged dried samples, to- gether with the data cards, were sent by airmail to the Applied Fisheries Laboratory, University of Washington for further processing. At the Applied Fisheries Laboratory, the dried samples were ashed at temperatures up to 540°C, cooled, slurried, dried, and then counted in an internal gas-flow counting chamber. The counts per plate were converted to disintegrations per minute per gram (d/m/g) of wet tissue, as of the date of collection, by correcting for sample weight, geometry, backscatter, self-absorption, coincidence, and decay. For a more complete discussion of these procedures see WT-616 a UN ERs Cyn, = x ne