According to Rosemann, it is an essential condition for the acceptance of the Heiden-hain-Paylov theory of HCl formation, that the terminal acidity in any 1 experiment be not significantly lower than the highest value attained in that experiment. None of his own observations satisfied this condition. In the present contribution the terminal acidity is specifically defined for purposes of analysis as the acidity of that sample, the mean secretory rate of which is the same as that of the first sample in the experiment. It is then shown that the terminal drop in acidity is very small, and may be ascribed to a continuous secretion of mucus, pepsin, etc., throughout the experiment. Further, when the experimental conditions are such as to reduce this continuous secretion to a minimum, the terminal drop disappears; i.e., the constancy of acidity which Rosemann demanded as an essential consequence of the older theory can be demonstrated. Thus, the major argument on which Rosemann based his opposition to the Heiden-hain-Pavlov theory is refuted.