Dr. D. E. Lea's book The Action of Radiation on Living Organisms is certainly the best summary available in any language of what happens when X-rays, gamma rays, or rapidly moving electrons, alpha particles, neutrons, and so on, penetrate living tissue. An insect is, in one respect at least, much more of a machine than is a man or a mouse. We are also constantly replacing our blood corpuscles, by the division of cells in the bone marrow. So anaemia is another consequence of over-radiation. When a cell divides most parts of the new cell are made afresh. But some essential parts are copies of the corresponding parts of the old cell. Lea's most important work was a very careful comparison of the effects of different kinds of rays and quickly moving particles. He might have investigated the possibilities of protection from these effects by chemical agents.