» INTERNAL DEPOSITION OF RADIONUCLIDES and the analysis at 4 months represents only radiological decay. Thus, the results are not directly comparable to those obtained from ani- mals which were returned alive, and in which biological turnoveras well as radiological decay were operating. The largest fraction of the gross beta activity in the fish was contributed by the concentration of radioactive material in the viscera, In two of the fish in which bones and muscle were separated and analysed, equal amountsof activity were found in each fraction. However, the storage of these fish in formaldehyde for 3 months may have permitted the diffusion of the radioelements from bone to muscle to take place. Further studies on fresh fish will clarify this point. The contamination of the fish in the lagoon was considerably greater than that of the land animals studied. As fish form a large staple item in the diet of the Marshallese, the high level of contamination is important. At the end of a 214-month experimental period, the excretion by the chickens of both beta and gammaactivity per 24 hours was 5 percent of the value measured at the start at 37 days post detonation (Fig. 5.1). Analysis of pig excreta indicated a similar decrease of activity with time. In a 6-week period, the gamma activity excreted per 24. hours decreased to about 2.5 percent of the activity excreted at 44 days post detonation. The excreta of the pigs from Utirik contained less than 10 percent of the gross betn activity found in the excreta of the pigs from Rongelap at the same time. This ratio of 10 was approx- imately the same ratio found between the ac- tivity of the food, water and soil samples of the two locations. Radiochemical Analysis of Tissues and krereta. Radiochemical analysis of pig tissues indicated that 62 percent of the skeletal beta activity was derived from Sr*. 7 percent from Ba’*?, and 10 percent from the rare earth group at 82 days post detonation (Table 5.8). The radioisotopic composition of the urine at this time wassimilar to that of the skeleton. The distribution of activity in the body of the pig 81 may represent the distribution in humanbeings. The absolute amountof internal contamination in the Rongelap people wus, however, only a tenth of that found in the animals. At 4 months post detonation, the alkaline earths comprised less than 2 percentof the total activity in the clam (Table 5.10). The rare earth group constituted 33 percent of the total beta activity. The balance of the activity was contributed chiefly by Zr®5 (21 percent) and Ru? (32 percent). About 50 percent of the material found in the viscera of the fish was of the rare earth group. Very small amounts of strontium and barium were found. In the tissues of the tish, strontium, barium and the rare earths contributed only about 10 percent of the total activity. 5.43 Autoradiographs A numberof autoradiographs of the tibiae and femurs of 1 chick, 4+ pigs, 1 rooster and 2 chickens were prepared both at the USNRDL and at the Argonne National Laboratory (ANL) to determine the pattern of deposition of fission products. Contact printing on X-ray no-screen film was found to be the most satisfactory method of preparing the autoradiographs. The discussion and conclusions presented below summarize the tindings reported by Norris (15). The autoradiographof a tibia from a chicken sacrificed at 45 days post detonation (Fig. 5.2) indicated a relatively uniform distribution of the activity throughout most of the bone, with the highest concentration of activity in the area adjacent to the epiphysis. This aren of high activity corresponds to an area of dense trabecular bone. The tibia and femur of a baby chick, which died spontaneously 47 days post detonation, showed the heaviest concentration of radioac- tive material in the diaphysis (Fig. 5.3). The end regions of the bone, which were laid down after the animals were removed from the con- taminated environment, were relatively lacking inactivity. The region of greatest activity was in che diaphysis, which appeared to be ab-