EXPERIMENTAL RICKETS IN RATS : V. THE EFFECT OF VARYING THE ORGANIC CONSTITUENTS OF A RICKETS-PRODUCING DIET.

1. Casein phosphorus does not completely prevent the development of rickets when substituted in Diet 84 in amount equivalent to a protective dose of basic potassium phosphate. 2. The protection given by lecithin is equivalent to its phosphorus content. 3. The protection given by yeast is at least proportional to its phosphorus content. An amount carrying sufficient vitamine B to promote growth, but insufficient to provide adequate phosphorus, does not prevent rickets. 4. Vitamine A, in the form of butter or butter fat to the amount of 10 per cent of the diet, neither prevents nor cures rickets. 5. The substitution of 10 per cent of egg albumin in Diet 84 improves the nutrition, but does not prevent rickets. 6. The addition of meat to Diet 84, thereby supplying an abundance of phosphorus, promotes normal growth and normal bone formation. A diet consisting solely of meat and flour is inadequate for proper growth, and leads to changes in the bones comparable with those observed on a diet low in calcium, but rich in phosphorus. 7. A diet has been found which contains the necessary food elements for approximately normal growth, and in which the only known deficiency is phosphorus. This leads regularly to the production of rickets.