582 STRUCTURAL ANATOMY OF THE LIVER. 



plexus in its interior, the lobular biliary plexus, which constitutes the 

 principal part of the substance of the lobule. The ducts terminate 

 either in loops or in caecal extremities. 



The coats of the ducts are very vascular, and supplied with a 

 number of mucous follicles, which are distributed irregularly in the 

 larger, but are arranged in two parallel longitudinal rows in the 

 smaller ducts. 



The Hepatic artery enters the liver with the portal vein and hepatic 

 duct, and ramifies with those vessels through the portal canals. Its 

 branches are the vaginal, interlobular, and lobular. The vaginal 

 brandies, like those of the portal vein and hepatic duct, form a vaginal 

 plexus, which exists throughout the whole extent of the portal canals, 

 with the exception of that side of the smaller canals which corresponds 

 with the artery. The interlobular branches, arising from the vaginal 

 plexus and from the parietal side of the artery in the smaller canals, 

 ramify through the interlobular fissures, and are principally distributed 

 to the coats of the interlobular ducts. 



"From the superficial interlobular fissures small arteries emerge, 

 and ramify in the proper capsule, on the convex and concave surface 

 of the liver, and in the ligaments. These are the capsular arteries.' 1 '' 

 Where the capsule is well developed, " these vessels cover the surfaces 

 of the liver with a beautiful plexus," and " anastomose with branches 

 of the phrenic, internal mammary, and supra-renal arteries," and with 

 the epigastric. 



The Lobular brandies, extremely minute and few in number, are 

 the nutrient vessels of the lobules, and terminate in the lobular venous 

 plexus. 



All the venous blood resulting from the distribution of the hepatic 

 artery, even that from the vasa vasorum of the hepatic veins, is re- 

 turned into the portal vein. 



The Hepatic veins commence in the substance of each lobule by 

 minute venules, which receive the blood from the lobular venous 

 plexus, and converge to form the intralobular vein. The intralobular 

 vein passes through the central axis of the lobule, and through the 

 middle of its base, to terminate in a sublobular vein ; and the union of 

 the sublobular veins constitutes the hepatic trunks, which terminate 

 in the inferior vena cava. The hepatic venous system consists, there- 

 fore, of three sets of vessels ; intralobular veins, sublobular veins, and 

 hepatic trunks. 



The Sublobular veins are contained in canals formed solely by the 

 bases of the lobules, with which, from the absence of Glisson's capsule, 

 they are in immediate contact. Their coats are thin and transparent ; 

 and, if they be laid open by a longitudinal incision, the bases of the 

 lobules will be distinctly seen, separated by interlobular fissures, and 

 perforated through the centre by the opening of the intralobular vein. 



The Hepatic trunks are formed by the union of the sublobular veins ; 

 they are contained in canals (hepatic-venous) similar in structure to 

 the portal canals, and lined by a prolongation of the proper capsule. 



