W. E. Heston

Biological studies in the tolerance range.

The experiments to be discussed here were started early in 1941 and were greatly expanded during the war. Although they are not yet completed, it is not expected that the results will be altered significantly by future findings. Gamma rays were used throughout the experiments. The daily doses were 8.8 r, 4.4 r, 2.2 r, 1.1 r, and 0.11 r, given either in eight hours or twenty-four hours per day. Three radiation sources were used: 1 gm., 250 mg., and 100 mg. of Ra element filtered with 0.5 mm. of platinum. The shelves carrying the cages of the experimental animals were arranged so that each cage in a given set was approximately at an equal distance from the source for each exposure level. Figure 1 shows the experimental set-up used with the 1 gm. source. After the daily eight-hour exposure, the source was lowered underground into a shaft to a depth of 21 feet. In the two other experimental set-ups the shelves for animal cages were arranged similarly. The gamma ray sources were kept in lead boxes provided wit...