on~ o ™,. instrumentation irreproducibility or more likely, unsuspected diuretic factors, the measured specific K* activity in the urine is likely to vary considerably in the same individual. It is felt, therefore, that greater accuracy in the determination of the exchangeable fraction must await clarification of the apparent irreproducibility of the specific K* activity of the urine. V. Radium in Humans Cc. E. Miller There is seemingly a tendency to relate the radium burdens of former dial painters to the length of their employment in the radium dial industry. Information elicited during conversations with some of these former dial painters indicates that such a relationship does not exist. One individual disclosed that some of the girls painted their finger- nails, eyebrows, and even streaks in their hair with radium dial paint before going out on social dates, A second subject stated that the painters who taught new employees would eat a quantity of radium dial paint froma spatula to convince them that the material was harmless. Considering such practices, it should not be considered unlikely to find an individual with a current burden of Zc of Ra6 asa consequence of an employment period of only three months (prior to 1930) in the radium dial painting industry. To our collection of cases containing Ra”** as a result of © either employment or therapy two subjects have been added bearing 2.45 and 1.15 yg respectively. VI. Radioactivity in the Liver of a Tridacna Clam C.E. Miller On June’ 30, 1956, Dr. Theodore R. Folsom of the Scripps Institute of Oceanography, La Jolla, California, sent two samples from the liver of a Tridacna (killer) clam to this Laboratory for gamma-ray analysis. This clam had been collected May 18, 1956, prior to the tests of that year in the Bikini Lagoon, 1000 feet northwest of the shore of Bikini Island ata depth of 10 feet. The weight of the whole clam meat was estimated at 1.8 to2.0kg wet weight. The weight of the part saved for assay (commonly called the liver) was 171 grams wet weight and 29 grams dry weight, of which two samples weighing 5 and 7 grams were used for measurement. The gamma ray-scintillation spectra obtained from the 7-gram sample is illustrated in Fig. 24 wherein the top curve is the spectrum obtained from the gross sample. The low energy photopeak was identified as Co*” and 012138