STRUCTURAL ANATOMY OF THE LIVER. 581 



lobular. The vaginal branches are those which, being given off in the 

 portal canals, have to pass through the sheath (vagina) of Glisson's 

 capsule, previously to entering the interlobular spaces. In this course 

 they form an intricate plexus, the vaginal plexus^ which, depending 

 for its existence on the capsule of Glisson, necessarily surrounds the 

 vessels, as does that capsule in the larger canals, and occupies the 

 capsular side only in the smaller canals. The interlobular brandies 

 are given off from the vaginal portal plexus where it exists, and 

 directly from the portal veins, in that part of the smaller canals where 

 the coats of the vein are in contact with the walls of the canal. They 

 then enter the interlobular spaces and divide into branches, which 

 cover with their ramifications every part of the surface of the lobules 

 with the exception of their bases, and those extremities of the super- 

 ficial lobules which appear upon the surfaces of the liver. The inter- 

 lobular veins communicate freely with each other, and with the corre.- 

 sponding veins of adjoining fissures, and establish a general portal 

 anastomosis throughout the entire liver. The lobular branches are 

 derived from the interlobular veins ; they form a plexus within each 

 lobule, and converge from the circumference towards the centre, where 

 they terminate in the minute radicles of the intralobular vein. " This 

 plexus, interposed between the interlobular portal veins and the 

 intralobular hepatic vein, constitutes the venous part of the lobule, 

 and may be called the lobular venous plexus.' 1 '' The irregular islets of 

 the substance of the lobules, seen between the meshes of this plexus 

 by means of the microscope, are the acini of Malpighi, and are por- 

 tions of the lobular biliarj r plexus. 



The portal vein returns the venous blood from the chylopoietic 

 viscera, to be circulated through the lobules ; it also receives the 

 venous blood which results from the distribution of the hepatic 

 artery. 



The Hepatic duct, entering the liver at the transverse fissure, 

 divides into branches, which ramify through the portal canals, with 

 the portal vein and hepatic artery, to terminate in the substance of the 

 lobules. Its branches, like those of the portal vein, are vaginal, inter- 

 lobular, and lobular. 



The Vaginal branches ramify through the capsule of Glisson, and 

 form a vaginal biliary plexus, which, like the vaginal portal plexus, 

 surrounds the vessels in the large canals, but is deficient on that side 

 of the smaller canals near which the duct is placed. The branches 

 given off by the vaginal biliary plexus are interlobular and lobular. 

 The interlobular brandies proceed from the vaginal biliary plexus 

 where it exists, and directly from the hepatic duct on that side of the 

 smaller canals against which the duct is placed. They enter the inter- 

 lobular spaces, and ramify upon the capsular surface of the lobules, in 

 the interlobular fissures, where they communicate freely with each 

 other. The lobular ducts are derived chiefly from the interlobular ; 

 but to those lobules forming the walls of the portal canals, they pass 

 directly from the vaginal plexus. They enter the lobule, and form a 



