ABDOMINAL CAVITY 505 



the third part of its course, it dips behind the right border of 

 the head of the pancreas, and coming into relation with the 

 main duct of the pancreas it accompanies it into the wall of 

 the second part of the duodenum, where they both enter the 

 ampulla of Vater. The ampulla opens into the cavity of the 

 gut by a single orifice, which is situated on the duodenal 

 papilla. 



Dissection. Make a vertical incision in the anterior wall of the second 

 part of the duodenum, nearer its right than its left lateral border. At the 

 upper and lower ends of the vertical incision make short transverse incisions 

 and turn the flaps so formed aside. Clean the interior of the duodenum 

 with a sponge, and then examine the mucous membrane. Note that the 

 mucous membrane of the second part is thrown into numerous and large 

 plicce circulares, and that, as a rule, it is deeply stained by bile. Look for 

 a longitudinal fold of the mucous membrane, which lies at the junction of 

 the medial and posterior walls, nearer the lower than the upper end, this 

 is the plica longitudinalis. It serves as a guide to the duodenal papilla 

 which lies at its upper extremity, usually concealed by one of the largest 

 of the plicae circulares. Pass a small probe through the opening on the 

 apex of the papilla into the ampulla. Make an opening in the lower part 

 of the bile-duct, and pass a small probe along the duct into the ampulla ; 

 perform the same operation on the main pancreatic duct, then cut down 

 through the medial wall of the gut and open up the lumina of the ducts, 

 the cavity of the ampulla of Vater, and its orifice of communication with 

 the interior of the duodenum. 



Vena Portae (Portal Vein). Blood is carried to the liver 

 both by the hepatic artery and by the portal vein. The 

 hepatic artery which carries arterial blood has already been 

 examined, p. 445. The portal vein, which carries the venous 

 blood from the whole of the abdominal part of the alimentary 

 canal, except the anal canal, and from the spleen, the 

 pancreas, and the gall-bladder, must now be studied. It is 

 a wide vessel, about three inches in length (7.5 c.m.), which 

 is formed by the union of the superior mesenteric and splenic 

 veins behind the neck of the pancreas, and between it and 

 the upturned uncinate process of the head of the pancreas. 

 It ascends, behind the first part of the duodenum and in 

 front of the inferior vena cava, to the lower margin of the 

 epiploic foramen where it leaves the vena cava, enters the 

 lesser omentum, and continues upwards, in front of the 

 epiploic foramen and behind the bile-duct and the hepatic 

 artery, to the right extremity of the porta hepatis ; there, 

 after enlarging slightly, it divides into a wide short right 

 branch, and a longer and narrower left branch. The right 

 branch receives the cystic vein and then enters the right 



