The rôle of acidity in digestion depends on the H-ion concentration rather than on the itratable acidity. In experiments with normal breast-fed infants, Marriott and Davidson1 came to the conclusion that optimum gastric acidity was reached one and one-half hours after feeding and was maintained for one hour. The range of H-ion concentration during the period of optimum gastric digestion was found to be from pH 3.5 to 5, the average being pH 3.75.
With an increase in the age of infants there is a gradual increase in the H-ion concentration, while disease, malnutrition and infections generally lower the H-ion concentration attained in the stomach.
Cow's milk has a relatively great buffer capacity over the range of H-ion concentration concerned in digestion, and therefore requires a relatively high gastric secretion as compared with that necessary when infants are breast fed.1
Attempts have been made to modify cow's