The observations of Opie1 and others have established that in about 25 per cent of normal persons the ends of the common bile and main pancreatic ducts join at or before the papilla of Vater, resulting in a confluence of the secretions of these two ducts, the "common channel." Thus the anatomic arrangement is such that a calculus at the outlet, a spasm of the sphincter of Oddi or edema of the duodenal mucosa may cause reflux of the secretion from one into the other duct. That reflux of bile into the pancreatic duct may be an important factor in the causation of acute pancreatitis in some cases seems well established. More recently considerable evidence has accumulated to indicate that the flow may be reversed, i. e., that there can be a reflux of pancreatic juice into the biliary tract.2 The strongest evidence that this occurs has been