It is proposed that the choleretic actions of the gastrin-like peptides -- gastrin, cholecystokinin, and caerulein -- be investigated by determining if these agents stimulate ductular or canalicular bile formation. Since recent experiments suggest an important nonvagal mechanism in insulin choleresis, it is thought important to determine more precisely how insulin stimulates bile secretion by estimating canalicular bile production after insulin, before and after vagotomy. The role of the vagus nerves in the regulation of hepatic bile secretion is poorly defined. The effects of vagotomy on ductular secretion will be determined by comparing secretin dose response curves before and after vagotomy. In addition, an assessment will be made of the effect of vagotomy on canalicular secretion by performing dose response tests of sodium taurocholate administered intravenously before and after vagotomy.