No unanimity of opinion exists among students of rickets concerning its cause. Heredity, dietetic errors, faulty hygienic conditions, infections of a microbial or other nature, and disturbances of the endocrin glands, have all been incriminated as the causative agents. At the present time two schools of investigators are essentially monopolizing the field in the study of this disease. One holds that it is essentially a condition brought about by errors in the diet, although admitting that unfavorable living conditions of any kind may play a role in that they depress the metabolic functions and cause the child to show more readily the effects of faulty nutrition than it would under more favorable conditions. The other school supports the view that hygienic conditions, especially lack of sunlight, and not dietetic factors, play the dominant role in the etiology of the disease. It seems possible to offer an explanation which brings into harmony most of the observations upon which the diverse interpretations have been placed.