The operation of partial gastrectomy has furnished an opportunity for the study of many of the problems of gastric physiology. The present paper is not primarily concerned with the results following this procedure. These have recently been discussed by Berg,1 who introduced the operation in this country as the procedure of choice in the treatment of gastric and duodenal ulcer. But in spite of the numerous advances in physiology and their evident bearing on the subject, there still exists an apparent misunderstanding of the mechanisms involved. Since considerations of function are at least as important as those of structure, it may not be amiss to emphasize again the underlying facts and at the same time add some clarifying experiments. The first point to grasp is that the gastric secretion following a meal is not a single response to one type of stimulus. It is the total of responses to