Studies on inorganic salt metabolism.

Studies on inorganic salt metabolism in dogs and rats which have been in progress in this laboratory during the past two years indicate that a bone condition comparable in all essential respects to that seen in rachitic children may be produced in young puppies on a diet, which, as far as we have been able to determine, is adequate in respect to protein, fat, carbohydrate, inorganic salts and vitamins but possesses a high potential alkalinity; while parallel experiments with the same diets on rats have invariably resulted in normal bone development.

Our basal diet consisted of bread, cooked lean beef, skimmed milk powder, butter fat and fresh orange juice made into a mush with distilled water. To this was added a salt mixture, the composition of which was based on ash analyses of cow's milk, except that the phosphorus was omitted and different proportions of calcium were used. The phosphorus content of the diets was varied by adding dibasic potassium phosphate to the above salt mixture, and the degree of alkalinity regulated by the addition of HCl. The first lot of salt mixture prepared proved to be alkaline in reaction and when added to the food mixture as described above and fed to six young puppies resulted in severe rickets in all cases, our diagnosis being based upon blood and bone analyses for calcium and phosphorus, radiographic, clinical and histological evidence. The parallel experiment on rats was negative. Another group of three puppies of the same litter received the identical diet with the addition of 0.8 gm. of phosphorus daily. They too developed rickets, the clinical signs appearing earlier than in the former group, while the rats fed similarly were normal.