THE NITROGEN PART1IION IN NEWBORN INFANTS' URINE BY

Ther appears to be very little information on the partition of nitrogen in the urine of infants during the first week of life comparable to the figures produced by Folin (1905a), and by subsequent workers for adult urine. Simon (1911), however, showed that the amino and undetermined nitrogen formed a greater proportion of the total urinary nitrogen in newborn infants than in adults. Schloss and Crawford(191 l)measured the total nitrogen, uric acid, and purine excretion in newborn infants, and found that the output of uric acid rose considerably during the first three days of life, and subsequently felL Most of the work on nitrogen metabolism in infancy has been done on infants aged two weeks or more, by which time life has become more stable. Colostrum has given place to milk, and the intake of the latter is no longer rising very fast. The physiological dehydration of the first few days has passed, and meconium is no longer being excreted. Studies in nitrogen metabolism made during the first few days of life have, however, a particular value, for they help to bridge the gap between foetal and postnatal metabolism. Unfortunately, the quantities of metabolites excreted during the first few days of life are not necesarily the same as those actually produced by the organism, for Balint and Stransky (1920) and McCance and Widdowson (1947) have shown that the dehydration during the first three or four days of life is accompanied by a rise in the urea and non-protein-nitrogen in the body fluids. Consequently, the end products of nitrogen metabolism will not be excreted so rapidly as they are produced during the first three or four days, and rather more rapidly during the ensuing days. The present work was undertaken to provide further information on the partition of nitrogen in the urine of very young infants, and on their daily output of certain nitrogenous substances