The terminal portion of the bile duct of the guinea pig was surrounded by the circular muscle fibers which were ramified from the same layer of the duodenum. The orifice of the common bile duct was opened by the rewinding action of the muscle contraction and a small amount of bile which was in the terminal portion of the bile duct was expelled.
The intraluminal pressure of the distal end of the common bile duct had an important role on the bile expulsion. When the intraluminal pressure of the ampulla overcame the resistance of the sphincter which was formed by the circular muscle, some bile in the ampulla was forced to expel into the duodenum, but a large amount of bile was pushed back into the common bile duct. The pace-maker area exsisted in the common bile duct near the ampulla.
The excitation waves travelled down to the ampulla at the speed of 30-50 mm/sec.
It seemed likely that the so-called Oddi's sphincter did not exsist independently with the duodenal muscle, but some sphincter mechanism might exsist.