Some Biological Effects of Continuous Gamma Irradiation, with a Note on Protection

The experiments detailed in this paper were begun in December 1935, and deal with the after-effects of γ radiation on young rats, particularly with reference to their breeding capacity, as it is well known that the generative system is particularly sensitive to radiation, and may be profoundly affected by moderate exposure to γ rays, leading to permanent sterility. It was decided to find out how much continuous γ radiation young rats would tolerate without any obvious effect on their of growth and subsequent fertility. Nearly 150 young rats, all of the same breed, about six to ten weeks old, varying in weight from 50 to 100 grammes, were set aside for this experiment. The radium (148 mgm. of element in platinum tubes—the thickness of these ranged from 0·3 to 2·0 mm.) was packed into a brass box 2 mm. thick and 6·2 cm. square; this was fitted and sealed into a bracket surrounded by 2·5 cm. of lead, which screened the radium in such a fashion that, though the cone of radiation was large enough to reach well beyond the cages of the experimental rats, the rest of the rats in the animal house were effectively screened. This contrivance was fixed 50 cm. above the top shelf (A) on which two cages of rats (one holding males and the other females) were kept. On the next shelf (B) at 107 cm. from the radium source there were two more cages of rats.