Respiratory Metabolism in Infancy and in Childhood

In a previous study of the basal metabolism of premature infants¹it was noted that when the infants were on a diet of human milk the nitrogen in the urine collected for short periods while the infants were in the respiratory chamber represented only 5 per cent of the total heat production.²When cow's milk was used, the urinary nitrogen increased to represent 17 per cent of the total calories. These findings seemed to confirm the popular conception that the protein of human milk is better suited for retention by the growing human organism than the protein of cow's milk. This conclusion is, however, unwarranted, since the infants on the two types of diet received protein differing not only in quality but also in quantity. Observations were therefore planned in which the retention of nitrogen by premature infants fed human milk and that by premature infants fed formulas