CIRCADIAN RHYTHMICITY IN THE SENSITIVITY OF TWO STRAINS OF MICE TO WHOLE- BODY RADIATION

When male mice of the Swiss-Webster and C 3 H strains are maintained on a light-dark cycle in which the light begins at 7 a.m. and ends at 7 p.m., they are more sensitive to whole body x-irradiation (800 to 900 roentgens) given at 2 a.m. than at any other time in the cycle tested.