CAN X-RAYS BE USED TO INCREASE LITTER SIZE IN THE MOUSE?

1. The average litter size for normal CF1 mice is close to 10.5, varying in these experiments from 9.75 to 11.73. Separate groups of controls were provided for each of the three major experiments.2. Resorptions were found even among the control groups, with an average of 1.5%. Other anomalies were not encountered, even in offspring from irradiated ova. Resorptions following X-radiation of ovarian ova never exceeded 7%, which is still within the normal range.3. Depending upon the experiments, sexually mature females were either taken at random with regard to their estrous cycle, or vaginal smears were made and the females categorized to select the particular phase of estrous cycle of concern.4. Among litters from matings immediately after (whole-body) X-radiation from 10 to 200r, the variations in resorptions over exposure levels was minimal, while variation in average litter size was within the range of normal experience for these mice.5. Even among mice mated one week after exposure the differences in li...