522 STRUCTURAL ANATOMY OF THE LIVER. 



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 superficial lobules which appear upon the 

 surfaces of the liver. The interlobular veins communicate freely with each 

 other, and with the corresponding veins of adjoining fissures, and establish 

 a general portal anastomosis throughout the entire liver. The lobular 

 b ranches '-are derived from the interlobular veins ; they form a plexus with- 

 in 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." The irregular islets of the sub- 

 stance of the lobules, seen between the meshes of this plexus by means of 

 the microscope, are the acini of Malpighi, and are portions of the lobular 

 biliary 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, interlobular, 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 

 branches proceed from the vaginal biliary plexus \vhere it exists, and 

 directly from the hepatic duct on that side of the smaller canals against 

 which the duct is placed. They enter the interlobular 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 w r alls of the 

 portal canals, they pass directly from the vaginal plexus. They enter the 

 lobule, and form a 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 csecal extremities. 



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

 ber 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 branches, 

 like those of the portal vein and hepatic uuct, 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 

 ciucts. 



"From the -superficial interlobular fissures small arteries emerge, and 



