The evidence presented indicates clearly that the feeding of colostrum is responsible for the proteinuria. Observations on many calves killed within the 3 first days have shown that this condition is nearly universal and that it disappears after the 3rd day, even when the calf is not quite normal. Urine of fetuses and unfed calves did not contain it. By feeding different amounts of colostrum, by withholding it for some hours after birth, and by giving it alternately with milk, the appearance of protein in the urine as to time and quantity was clearly a function of the colostrum fed. Serum replacing colostrum produced the same effect to a less pronounced degree. The permeability of the kidneys as determined in a routine way on healthy calves killed within the 1st week of life ceases after the 3rd day. In the two cases fed repeatedly with colostrum, proteinuria was demonstrated up to 6 days in one case. The regularity of its disappearance in calves normally fed indicates that more experiments are necessary to prove a longer period of permeability. The continued excretion of protein in such animals may be due to a slight lesion of the kidneys. There is but one reference to this subject which we have been able to find. Langstein and Neuberg in a study of levulose and allantoin in the urine of new-born calves mention the presence of albumin in six cases without, however, making any comments as to its origin or referring it to the ingestion of colostrum. According to various observers, albumin may be found in traces during the 4 first days in over 60 per cent of infants examined. Since the food has not been taken into consideration renewed observations are needed to determine if the relationship found in calves is also true for the human infant.