In the light of these experiments it is possible to understand the results of Sherman and Pappenheimer, and it is necessary to place upon them a different interpretation from that of these investigators. This matter is so important, not only from the standpoint of the etiology of rickets, but as an illustration of the necessity of very elaborately planned series of experiments in order that error may be avoided, that a short discussion of them will be of value.

Patent flour is one of the most deficient foods which enters into the human diet, being exceeded in this respect only by isolated foods such as starch, sugars, fats or polished rice. Bolted flour is rather poor in protein and this is of rather poor quality. It is very deficient in calcium, phosphorus, sodium, chlorin, iron and possibly also in potassium. The only essential inorganic element which it probably contains in amount sufficient to meet the needs of an animal is magnesium. Bolted flour is also very-deficient in the anti-neuritic substance (water-soluble B) as shown by the frequent occurrence of beri-beri among the people of Labrador and Newfoundland, where bread from this source is a principal article of food. It is exceedingly poor in fat-soluble A, and in the organic factor playing a role in the prevention of rickets. From the standpoint of human nutrition it is important also that it lacks entirely the anti-scorbutic substance. The basal ration employed by Sherman and Pappenheimer was deficient in all the factors enumerated above. In the presence of so considerable a number of defects in the ration it was obviously impossible to be certain which were operative in the production of the disease. In the light of their experience, Mc-Collum, Simmonds, Shipley and Park interpret the data of Sherman and Pappenheimer as follows (20).

When calcium was added to the basal ration a marked disproportion in the calcium-phosphate ratio was produced, the calcium being nearly optimal and the phosphorus very low. Fat-soluble A (an anti-rachitic substance) was almost lacking, and the conditions were such under which we should expect severe rickets to develop. When neither calcium nor phosphorus were added, the content of both these elements in the diet was that contained in bolted wheat flour, and the ratio was more nearly the optimum than after the calcium addition, and, accordingly, osteoporosis and not rickets should have developed. They did not state whether osteoporosis existed. The animals were sorely in need of calcium, yet its addition under these peculiar conditions caused the development of the syndrome of rickets which they would otherwise have escaped. The situation is analogous to the effect of adding 0.5 per cent of butter fat to diet 3133. The animals needed the fat-soluble A which it contained, but its addition under the peculiar conditions of composition of that diet increased the severity of the rickets which developed. This principle has not hitherto been conceived of by nutrition investigators, but it is one of fundamental importance. When the potassium phosphate in the experiments of Sherman and Pappenheimer, was added, the Ca:P ratio was again made more favorable and rickets was prevented. In this case, the diet was made to contain fairly satisfactory concentrations of both these elements, which tended to promote normal bone development.