Abstract
The anatomy of the extra-hepatic biliary system in the guinea pig is in general similar to that in other laboratory mammals, but that it possesses certain peculiar features. The system consists of hepatic ducts, gall-bladder, cystic duct and common bile duct; but the latter terminates in a dilatation, or ampulla, which is closely applied to the surface of the duodenum on its postero-superior aspect and is situated about 7 to 10 mm. beyond the pylorus. From near the distal end of this ampulla there arises a small duct which passes directly through the duodenal wall and terminates at the head of a papilla.
We have observed the functioning of these structures immediately after killing and in animals under barbital anesthesia. On turning up the liver we have always found the system distended with bile in both fed and fasting animals; in this condition its walls are translucent. During the observations the parts were kept moist with warm normal saline. With each peristaltic wave in the duodenum a constriction is initiated in the common duct just above its junction with the ampulla, obstructing the duct lumen, and this is followed by a contraction of the ampulla which completely empties it of its contents. After the wave has passed, both sphincter and ampulla relax; the ampulla then gradually refills with bile in about 20 seconds to 1 minute, the rate depending on the existing tension in the gallbladder and hepatic ducts. This cycle of events is repeated with the next peristaltic wave, the sphincter and the ampulla always contracting powerfully. Movements of the duodenum other than regular peristalsis were never accompanied by contraction of either sphincter or ampulla.
Faradic stimulation of the first part of the duodenum elicited a localized contraction without causing contraction of either sphincter or ampulla.
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