There is a constant and striking difference in the bacteriologic findings in the stool of the breast-fed and the artificially fed infant. In the stool of the former gram-positive bacilli predominate, while in that of the latter1 gram-negative, morphologically dissimilar organisms are in excess.
To ascertain the significance of this variation and its importance in the problem of infant feeding were the objectives of this investigation. The introductory phase—the study of lysozyme in human milk and its relation to the bacterial flora of the milk—was begun in 1934 and is the subject of this paper.
In 1931 Rosenthal and Lieberman2 reported the influence of lysozyme in the development of the intestinal flora of infants. They found a lytic principle in the stools of nurslings which they tested against cultures of gram-positive sarcinas. It was inactivated by heating at 65 C. for one and a half hours or by