For centuries men speculated about the process of gastric digestion, but Iate in the eighteenth and early in the nineteenth centuries physiologists, both physicians and laymen, began to accumulate experimental evidence about its nature. At the same time, others discovered that the stomach is capable of secreting a strong mineral acid, and the questions of how that secretion is produced and how it is controlled became enduring problems. A Iittle later, the discovery that an acid extract of dead gastric mucosa is capable of digesting meat put the study of gastric secretion and digestion on a firm mechanistic foundation. From that time to the present, physi ologists have assiduously investigated gastric secretion and digestion, with the result that knowledge ofthose topics is as comprehensive and penetrating as isthat about other physiological processes. In addition, that knowledge is the basis of discrimi nating and effective clinical practice. I have described the experimental study of gastric secretion and digestion for two reasons. The firstisthat the successes and some ofthe failures ofphysiologists over two centuries are important parts of intellectual history that deserve to be recorded. The second is that some of those who use the accumulated knowledge every day are curious about its genesis. I assume that my readers have the technical knowledge to understand what I have written. If my account does not fully satisfy their curiosity, I have provided references that will open the path to further study.