Effects of Low Doses of X-Rays on Embryonic Development in the Mouse

Summary Mouse embryos of the BALB/c strain were irradiated 7 1/2 or 8 1/2 days post-fertilization with 25. 50. or 100 r of × rays (doses lower than any heretofore investigated in detail), allowed to come to term, and then observed for changes in vertebral column and thorax. It was found (a) that there are different types of dose-effect curves for different abnormalities, and (b) that a dose as low as 25 r gives effects that are detectable even in relatively small samples.