Since the incidence and severity of rickets have markedly increased in many places within recent times, and essentially parallel with it there has been a marked deterioration of the teeth, associated with underdevelopment of the jaws, and an increased tendency to general physical inferiority, we must look to some change or changes in living conditions which have brought about these results. On investigation we find that the pastoral peoples of Asia, Arabia, Northern Africa and Abyssinia are essentially free from the disease. This would be attributed by many to the "natural" conditions of living. England and Scotland have a high incidence of the disease, yet localities are found in both countries where the condition is rare or unknown. Ireland, the climate of which differs but insignificantly from certain other places where rickets is common, contains districts where it is unknown. The dampness of western Ireland is so great as to interfere seriously with the curing of forage crops for hay, yet the lack of sunlight does not promote rickets in the children, nor does the "black house" of the Hebrides, an extreme condition of lack of illumination and ventilation, cause the disease. It can be produced in animals under conditions in which all factors other than diet are eliminated, and in an animal, the rat, which is nocturnal in habits, and ordinarily lives under conditions of extreme filthiness, darkness and bad air without showing the least deviation from the normal in the structure of its bones. We must look, therefore, to our methods of feeding pregnant mothers, lactating mothers, and infants and children, if we are to accomplish our purpose of eradicating this disease which stands first in importance in causing physical inferiority of the human race in Europe and America. We have in rickets another incrimination of the milled cereal, tuber and muscle meat type of diet. The progress in specialization in the direction of limiting the food supply largely to these classes of articles, is synchronous with the increase in the occurrence of rickets. Wrong dietary habits are the cause of rickets, and also of faulty tooth development, and of vulnerability of the teeth, which now is causing so much alarm.