The important functions that have been assigned in experimental and clinical medicine to radiant energy of certain wavelengths have given tremendous impetus to researches in this field. The rôle of ultraviolet radiation in metabolism and the relationship between this type of radiation and vitamin D are observations that not only stimulate the scientific mind but appeal to the imagination of the public at large. This, unfortunately, has resulted in much commercialism and has set up a false conception of radiant energy as a panacea. Sunlight or artificial radiation is not a specific form of treatment and should not be used without medical guidance and adequate equipment. This form of therapy may play a prominent part in certain abnormal conditions; it is of minor importance in the life of normal persons who are provided with a completely adequate diet.
The proper use of radiation and irradiated materials has often caused remarkable