PHYSIOLOGICAL ANATOMY OF THE LIVER 357 



Branches of the Portal Vein, the Hepatic Artery and the Hepatic Duct. 

 These vessels follow out the branches of the capsule of Glisson, become 

 smaller and smaller, and they finally pass directly between the lobules. In 

 their course, however, they send off lateral branches to the sheath, form- 

 ing the so-called vaginal plexus. The arrangement of the vessels in 

 the sheath is not in the form of a true anastomosing plexus, although 

 branches pass from this so-called vaginal plexus between the lobules. 

 These vessels do not anastomose or communicate with each other in the 

 sheath. 



The portal vein does not present any important peculiarity in its 

 course from the transverse fissure to the interlobular spaces. It sub- 

 divides, enclosed in its sheath, until its small branches go directly 

 between the lobules; arid in its course it sends branches to the sheath 

 (vaginal vessels), which afterward go between the lobules. The hepatic 

 artery has three sets of branches. As soon as it enters the sheath with 

 the other vessels, it sends off minute branches (vasa vasorum) to the 

 walls of the portal vein, to the larger branches of the artery itself, to 

 the walls of the hepatic veins, and a rich network of vessels to the 

 hepatic duct. In its course the hepatic artery also sends branches 

 to the capsule of Glisson (capsular branches), which, with branches of 

 the portal vein, go to form the so-called vaginal plexus. From these 

 vessels a few arterial branches are given off, which pass between the 

 lobules. The hepatic artery can not be followed beyond the interlobular 

 vessels. The terminal branches of the hepatic artery are not directly 

 connected with the radicles of the hepatic veins, but they empty into 

 small branches of the portal vein within the capsule of Glisson. 



Interlobular Vessels. Branches of the portal vein, coming from the 

 terminal ramifications of the vessel within the capsule and from the 

 branches in the walls of the capsule, are distributed between the lobules, 

 constituting the greatest part of the so-called interlobular plexus. These 

 are situated between the lobules and surround them ; each vessel, how- 

 ever, giving off branches to two or three lobules, and never to one 

 alone. They do not anastomose and consequently are not in the form 

 of a true plexus. The diameter of the interlobular vessels varies between 

 -j-^o- and y o of an inch (17 and 34 /*). In this distribution, the blood- 

 vessels are followed by branches of the duct, which are much fewer 

 and smaller, measuring only ^W of an incn ( IO /*) an( ^ some, even, 

 have been measured that are not more than ^Fo f an * ncn (8>) in 

 diameter. 



Lobular Vessels. From the interlobular veins eight or ten branches 

 are given off which penetrate the lobule. As the interlobular vessels 

 ramify between different lobules, each one sends branches into two and 



