Experimental production of rickets with diets of purified food substances.

The possibility of producing experimentally in animals symptoms essentially identical with those associated with rickets in human beings promises to advance the study of this disease greatly. The efforts in this direction have hitherto been concerned with the effects of diets of varied composition—usually for the most part mixtures of natural foods or materials derived therefrom without much manipulation. This has made comparisons between different rations somewhat difficult and often unconvincing because with a change in the natural foods several chemical ingredients are altered at the same time and consequently the cause of any marked change induced thereby in the animal usually cannot be charged directly to changes in any one chemical factor. For example, Sherman and Pappenheimer have demonstrated that rickets is brought about in a few weeks in rats by a diet of patent flour 95 per cent plus a mixture of three inorganic salts (Ca lactate 2.9 per cent, NaCl 2.0 per cent, Fe citrate 0.1 per cent). In experimental feeding tests under otherwise comparable conditions we found that the introduction of 10 per cent of a protein (lactalbumin was used) to replace an equal weight of flour in the Sherman-Pappenheimer ration increased the severity of the symptoms. The calorie value of the two foods was essentially alike. One diet was made far richer than the other in protein of good biological quality; but this result was attended with “dilution” of the flour so that the various food factors which it specifically introduced into the diet, viz., phosphates and certain other inorganic ingredients, vitamines, and carbohydrates, were decreased. Were the gains or the losses responsible for the increased severity of the rickets? Obviously the physiological “analysis” or interpretation becomes complicated where several food factors are altered by an even seemingly simple change in the diet.