Comparatively recent interest in ultraviolet rays as a means of sterilization stimulated us to investigate the value of this therapeutic method. The fountainhead of interest in the beneficial effects of ultraviolet irradiation of blood is E. K. Knott,1 who, working from the premise that ultraviolet rays have bactericidal properties, devised an ingenious apparatus for the purpose of irradiating whole blood. He recognized early "that the source of the ultraviolet energy was inconstant and varied widely" and would "produce variable results and often a failure to obtain measurable results." Because of this, "A source of ultraviolet of known intensity was sought that could be easily controlled so that a uniform dosage could be achieved and duplicated at will."
When animal experiments were first begun, the animals died of overirradiation. Eventually the premise was evolved, from experiments on bacteremic animals, "that it was neither necessary to expose the