The Reaction of the Mouse Spleen to X-Rays Measured by Changes in Organ Weight

Carter et al. (1) were the first to use changes in the weight of the spleen and thymus as a measure of radiation dose. They exposed young mice to total-body irradiation and measured the changes in organ weight 5 days later. The method has been used extensively by the Los Alamos group (1-3) to determine the RBE (relative biological effectiveness) of neutrons and ~-rays compared to 250-kv X-rays. Prior to using the principle of this method for the determination of the RBE of 1 and of 70-Mv X-rays, and because of our interest in the physiology of such reactions, a critical study has been made of the change in weight of the thymus and of several factors likely to influence it, after exposure of mice to 250-kv X-rays.