After seven years' experience in supervising the examination of applicants for hazardous occupations, and a careful study of the literature, I am attempting here to present most of the known facts, and some of the problems still to be worked out, in the field of color blindness.
In train, yard and engine service on railways, in certain marine occupations, and to a less extent in other industries, color blindness is a hazard which has not received the thoughtful and accurate consideration which safety demands. Our navy, the Public Health Service, and especially European railway surgeons, have called attention to the insufficiency of methods in common use for detecting this defect, yet the safety of employees and the traveling public is still too often entrusted to incompetent examiners armed with improper apparatus.
A knowledge of the physics of light and the physiology of color perception is taken for granted. Attention is