106 PRACTICAL MICROSCOPY. 



THE LIVEE. 



This great gland is covered with a fibrous membrane the capsule 

 of Glisson. The capsule is covered with a single layer of irregularly 

 shaped, flat epithelial cells. 



Prolongations from the fibrous, visceral portion of Glisson's capsule 

 penetrate the organ from every side, and divide the entire structure 

 into compartments, the lobules. 



The hepatic lobules are irregularly polygonal in transverse section, 

 and somewhat ovoid vertically. They are about one-twelfth inch in 

 diameter. 



Let us first examine the general plan of the vascular arrangement, 

 and later, the minute structure of the lobular parenchyma. 



The hepatic blood-supply comes from two sources: 1st, The venous 

 drainage from the chylopoietic viscera collected in the portal vein. 

 2d, ArterialJ supply, provided directly from the aorta by the hepatic 

 artery. The portal venous blood is filtered through the liver instead 

 of passing directly to the ordinary destination of such blood (the 

 cava), in order to contribute certain factors to the processes of diges- 

 tion and metabolism, while the smaller arterial supply is distinctly 

 nutritive. The hepatic duct is the common excretory conduit of the 

 bile after its formation by the parenchyma from, mainly, the portal 

 blood. 



The scheme of the organ will be understood by reference to Fig. 

 77, which is purely diagrammatic. 



The portal vein enters the liver at the transverse fissure. It divides, 

 subdivides, and, reaching every part of the various lobes, the terminal 

 twigs are seen in the connective tissue of the walls of the lobules. 



Branches from these portal termini or interlolular veins penetrate 

 the lobular areas, and immediately break up into capillaries, which 

 form an intricate plexus throughout the lobule. The blood from 

 these capillaries is finally collected in a central or intralobular vein, 

 by means of which it is immediately drained from the lobule. 



The central veins, from a number (varying) of the lobules, unite 

 outside of the latter, forming the beginning of the hepatic or so-called 

 sublobuldr vein*; and, like vessels from other lobular areas, unite, 

 forming several (six or seven) large hepatic vein* which, passing in the 

 connective-tissue framework, finally drain the blood from the organ 

 and pour it into the ascending cava as it lies posteriorly in its fissure. 



