Reflex Control of Gastric Secretion

Without considering the possibility of any alternative, nineteenth-century physi­ologists assumed that gastric secretion is exclusively under nervous control, and that it is under reflex control was amply demonstrated toward the end of the century by Ivan Petrovich Pavlov and his students. The doctrine of exclusive nervous con­trol was shattered by William Bayliss and Ernest Starling’s discovery on the after­noon of 16 January 1902 that a “chemical reflex” originating in the intestinal mucosa mediates stimulation of pancreatic secretion by acid in the upper intestinal tract. Spurred by this discovery, J. S. Edkins thought that he had identified a cor­responding humoral agent, gastrin,in the antral mucosa that mediates stimulation of acid secretion in the stomach. The twin discoveries that histamine is a powerful stimulant of acid secretion and that histamine is present in tissue extracts raised doubts about the reality of gastrin. Confusion on this point continued until just before the Second World War, when Simon Komarov presented some proof of the existence of gastrin, and beginning shortly after the end of the war, study of stim­ulating and inhibiting hormones dominated the problem of the control of gastric secretion. Toward the end of the period under consideration here, the interaction of nerves, histamine, and hormones in control of gastric secretion began to be understood.