A discovery of great importance in this connection was recently made by McCollum, Simmonds, Shipley and Park (20) who observed that the ratio between the concentration of calcium and of phosphorus in the diet may, within certain limits, be of greater significance to the welfare of an animal than the absolute amounts of these substances which the diet contains.

335. Sherman and Pappenheimer's Observation on Rickets. Sherman and Pappenheimer (21) have recently described the production of rickets by a diet deficient in phosphorus, and its prevention by the administration of a phosphate. Their data would lead one to the conclusion that the disease is brought about by phosphorus starvation. The isolated observation of these investigators is of special interest in that it is explainable on a very different basis from that which they had in mind. Sherman and Pappenheimer fed groups of young rats on the following diets, and with the results noted:

Wheat flour, sodium chlorid, 2%. No rickets.

Wheat flour, sodium chlorid, 2%, Ca Lactate, 3%. Rickets.

Wheat flour, sodium chlorid, 2%, Ca Lactate, 3%, K2HPO4, 0.4%. No rickets.

Instead of lack of phosphorus, per se, being the cause of the rickets in their animals, McCollum, Simmonds, Shipley and Park (20) regard the cause as due to an unfavorable ratio between the calcium and phosphorite, in the absence of sufficient of the or-ganic factor which plays a role in the production of this syndrome. The reasoning on which this conclusion rests was based upon experimental data which is of great interest in illustrating one of the several dietary situations which may give rise to rickets or similar conditions. The results of feeding the following diets will illustrate this principle.

Ration 3127

Rolled oats ......... 40.0

Gelatin ........... 10.0

Wheat gluten ........ 7.0

NaC l ............ 1.0

KC l ............. 1.0

CaC03 ............ 2.0

Dextrin ........... 39.0

Ration 3133

Rolled oats ......... 40.0

Gelatin ........... 10.0

Wheat gluten........ 7.0

NaCl ............ 1.0

KC l ............. 1.0

CaC03 ............ 2.0

Dextrin ........... 38.5

Butter fat .......... 0.5

Ration 3127 was markedly deficient in phosphorus and in fat-soluble A (anti-xerophthalmic substance), but was otherwise well constituted. Its proteins were of good quality, and its content of calcium not far from the optimum. Young rats fail to grow on this food, and develop severe ophthalmia. They cannot live many weeks on this diet because of the severity of the ophthalmia which develops.

Ration 3133 is essentially like Ration 3127, but contains 0.5 per cent of butter fat, which was added to defer the onset of ophthalmia and prolong the lives of the animals. This amount of butter fat did not suffice to protect against ophthalmia, but delayed its advent and diminished its rate of progress, and therefore increased the life and made possible, presumably, a greater amount of growth in the skeleton than was possible on diet 3127.

Both of the rations just described, in which the calcium content was optimal and the phosphorus and fat-soluble A very low, produced in young rats a pathological condition essentially identical with that found in human subjects of rickets. The lesions were more severe in animals fed Ration 3133 because of the small addition of butter fat, which functioned as described above.