Every one who deals with gastric contents in an analytic way is familiar with the observation that they are highly changeable in reaction. Specimens that are removed for examination are likely to show quite wide variations in acidity, ranging from an almost complete absence of "free" hydrochloric acid to a content approaching 0.4 or 0.5 per cent. Studies in the physiology of gastric secretion have made it clear that such marked differences are not due to corresponding variations in the acid strength of the fluid secreted at successive intervals by the gastric glands. Indeed, there is reason to believe that the gastric juice itself exhibits a surprising uniformity of reaction approximating 0.5 per cent. Consequently the lower values that are so commonly observed must be due to some diluting or neutralizing effects associated with events within the alimentary tract itself.
It has long been known that protein combines with acid