In a previous paper1 a study was made of the mineral and nitrogen retained by a premature infant per kilogram of gain in weight. In this paper the same method of study has been carried out, with few modifications, on two normal full-term infants, one fed on cow's milk and one on breast milk. The object of this study is to determine the mineral balances over a period long enough to obtain true representative values of the several mineral and nitrogen retentions per unit of growth.
Within the last few years several interesting papers on this subject have been published, especially by Rominger and Meyer2 and Rominger, Fasold and Meyer3 and also by Boldt, Brahm and Andresen.4 The balance experiments of these authors do not lend themselves entirely for comparison with those presented here, since in most of their experiments only calcium and phosphorus were determined