This volume is a treatise on photodynamic action and radiation, both artificial and natural, on the human being and on animals. It deals with diseases produced in men and in animals by radiation. The book contains a generous review of the literature on this rather restricted branch of medicine and embraces material contributed by the author himself especially regarding the use of radiation in cancer. The volume is in four parts and has a total of twenty-four chapters. Part one, the introduction, deals with the physical nature of radiation and its biologic effects. The second part is on photodynamic action. Diseases produced by light on domestic animals and on man are dealt with in parts three and four, and this material should be of interest to the dermatologist. Mathematical and chemical equations are sprinkled here and there, together with a goodly number of tables and charts. One chapter is given