The main facts concerning the acquisition and character of the bacteria which are harbored in the human intestinal tract have been established and are documented in the work of Woodward,1 Escherich,2 Schild,3 Szego,4 Tissier,5 Herter6 Mannaberg,7 Logan,8 Kendall,9 Rettger and Cheplin,10 van der Reis11 and others.
We know that the meconium is generally sterile at birth, that various bacteria appear in it within the first twenty-four hours of life, that the flora of the first three or four days is complex, that simplification accompanies the establishment of normal lactation and nursing and the appearance of the characteristic milk stool, and continues as long as the nursing baby is in good health, that diversification in the flora accompanies intestinal disturbances during the nursing period and normally follows weaning and the substitution of a more varied diet, and that even in