While I am by no means willing to agree with Bunge[114] that the chief importance of the acid of the gastric juice is its action as an antiseptic, I am decidedly of the opinion that the lack of free hydrochloric acid in the stomach-contents is more liable to cause disturbance through the consequent unchecked development of bacteria than through lack of proteolytic action, assuming, of course, the presence of a reasonable amount of combined HCl. The hydrochloric acid of the gastric juice unquestionably plays a very important part in checking the growth and development of many pathogenic bacteria, as well as of less poisonous organisms, which are taken into the mouth with the food. On all, or at least on nearly all of these organisms, hydrochloric acid exerts a far greater destructive action when free than when combined with proteid matter. As Cohn[115] has plainly shown, both hydrochloric acid and pepsin-hydrochloric acid quickly hinder acetic- and lactic-acid fermentation, but when the acid is combined with peptone, for example, it is no longer able to exercise the same inhibitory influence. It is also important to note that the lactic-acid ferment is not so sensitive to hydrochloric acid as the acetic-acid ferment. Consequently, when lactic-acid fermentation is once developed a comparatively large amount of HCl is required to arrest it. Hence, as we all know, a diminished secretion of hydrochloric acid renders possible acid fermentation of the stomach-contents, as well as putrefactive changes which would not occur in the presence of free HCl, and which are very incompletely checked when the acid is over-saturated with proteid matter. [114] Physiologische und Pathologische Chemie, p. 153. [115] Ueber die Einwirkung des künstlichen Magensaftes auf Essigsäure-und Milchsäure gährung. Zeitschr. f. physiol. Chemie, Band 14, p. 75. See also Hirschfeld: Pflüger’s Archiv f. Physiol., Band 47, p. 510. Pepsin-proteolysis, however, may proceed, to some extent, at least, even though a small amount only of combined acid is present. The combined acid, however, must be hydrochloric acid, if proteolysis is to be at all marked. To be sure, pepsin will act in the presence of lactic acid, as well as in the presence of other organic acids, and inorganic acids, likewise, but such action at the best is considerably weaker than the action of pepsin-hydrochloric acid.[116] [116] Chittenden and Allen: Influence of Various Inorganic and Alkaloidal Salts on the Proteolytic Action of Pepsin-Hydrochloric Acid. Studies in Physiol. Chem., Yale University, vol. 1, pp. 91, 94.