Abstract
Female rabbits were irradiated from a radiocobalt source on various days of pregnancy and examined three to five days before delivery. Following irradiation at 400 r, on days two, four or six before implantation, 24% of the embryos implanted and 19.9% developed into apparently normal fetuses; on day seven or eight at the time of implantation or soon after, all embryos died although 61% implanted; on days 9, 10 or 11, 16.5% of the embryos developed into living fetuses with high incidences of short tail and cleft palate and with low incidences of abnormal forelimbs, fused digits of forelimbs and exencephalia; on days 12, 13 or 14, 35% of the embryos developed into fetuses with a high incidence of fused digits in the foreβ or hindβlimbs; on days 15 to 22, 30% of the embryos developed into living fetuses without gross abnormalities.
Irradiation at 250 r on day eight did not cause death of all embryos as it did at 400 r. With irradiation at 250 r on days 8 to 14, 51 to 60% of the embryos developed into living fetuses with low incidences of abnormalities.
The size of fetuses was reduced very little following irradiation on days two to six or on days 18 to 22. But the size is distinctly reduced following the irradiation on days 11 to 16.
Necrosis of tissue, pycnosis of nuclei, and vacuolation of cells in the embryos were observed six hours after the irradiation of mothers at 400 r on days seven and eight.