GASTRIC MOTILITY: III. THE MECHANISM OF THE PYLORUS

I. RELATION OF ANTRAL CONTRACTION TO THE PYLORIC MECHANISM  Cannon's¹ theory of the acid control of the pylorus has long been accepted by numerous physiologists. Briefly stated—it will be referred to again later—he holds that the pylorus is closed during digestion, that an acidity of 0.2 per cent, on the gastric side brings about its opening, and that the presence of acid in the duodenum effects its closure. The antral waves sweep on repeatedly to the pylorus, but this gateway remains closed until the continued secretion of hydrochloric acid brings up the concentration of the acidity to the level indicated above. The pylorus then opens and the next advancing wave forces the antral contents into the duodenum.But after studying numerous dogs² by the method previously described, it seemed that this theory could not explain some of the observations that were made. For it became more and more