Relative Biological Efficiency of 1000-Kvp and 250-Kvcp X-Rays: V. Determinations Based on the LD 50 of the 4-Day-Old Chick Embryo

Abstract

The eggs, supplied by the Pioneer Hatchery, Petaluma, California, came from pure-bred White Leghorn stock. After collection from the nests they were stored in a cool room for less than 24 hours and were then shipped to the laboratory, approximately a 2-hour journey. The eggs were entered into experiments immediately (one experiment), or after storage at room temperature (70? to 75?F) for 1 day (four experiments) or for 2 days (one experiment). The duration of the storage period did not noticeably affect the results. Just prior to beginning incubation, the eggs were washed in a weak solution of detergent (Alconox, 0.5 gm/1) at 25?C, rinsed in water at 30? to 35?C, dried, and then numbered and weighed. After 72 hours of incubation at 37.6?C, during which the eggs were turned twice a day, the eggs were candled; those with normally developing embryos were returned to the incubator. Fertility averaged about 72 %. Eggs weighing more than 67 gm and less than 53 gm were discarded. The remainder was distributed in the various experimental groups so that all groups were alike with respect to average weight (60 gm) and distribution of weight.