In the fasting state, the secretions of isolated total gastric pouches were higher than what was found in classical gastric fistulae. Serum gastrin was lower in operated rats than in normal non-operated rats. The proximal duodenum would contain a substance which inhibited volume and acidity secretion and stimulated pepsin secretion. This role could be developed upon secretin and its family present in high concentration in the upper duodenum. If the vagus was necessary to volume and acid secretion, its action on pepsin secretion was strengthened by the proximal duodenum. After an intestinal meal, all secretions were enhanced, confirming the hypothesis that the intestine would contain an hormone which would act through the vagus, principally for volume and acid secretions and partially for pepsin secretion.