Medical science advances rapidly. New discoveries are announced frequently. This makes the physician's responsibility heavier and heavier. He has to know the old science and the new also. He has to know the power and the hazards of new devices and must use good judgment in balancing probable good against possible harm. Think of radiation! The engineers and the nuclear physicists keep developing new apparatus. New researches, including some by the health physicists and biologists connected with the development of the atom bomb, have taught us more about the hazards of the old apparatus, also, such as x-ray and radium. Even small quantities of roentgen or radium rays can prove damaging. Radiation injury to the skin sometimes leads to cancer, coming even many years after. Some of these patients did not show immediate injury, even so much as redness of the skin. Repeated or continuous irradiation of the whole body