1332 



THE ORGANS OF DIGESTION 



considerable size, which runs down the centre of the lobule from apex to base and is called the 

 intralobular or central vein (vena intralobularis) (Fig. 1076). At the base of the lobule this vein 

 opens directly into the sublobular vein, with which the lobule is connected, and which, as before 

 mentioned, is a radicle of the hepatic vein. The sublobular veins, uniting into larger and larger 

 trunks, end at last in the hepatic veins, which do not receive any intralobular veins directly. 

 Finally, the hepatic veins, as mentioned on page 754, converge to form three large trunks which 

 open into the inferior vena cava, while that vessel is situated in the fissure appropriated to it at 

 the back of the liver. The portal vein is the nutrient vessel of the parenchyma of the liver, 

 while the hepatic artery nourishes the vessels, ducts, and interlobular connective tissue. 



3. The Ducts. Having shown how the blood is brought into intimate relation with the 

 hepatic cells in order that the bile may be secreted, it remains now only to consider the way in 

 which the secretion, having been formed, is carried away. Several views have prevailed as to 

 the mode of origin of the hepatic ducts; it seems, however, to be clear that they commence by 

 little passages, which are formed between the cells and which have been termed intercellular 

 biliary passages, bile capillaries, or bile canaliculi (ductus biliferi). These passages are merely 

 little channels or spaces left between the contiguous surfaces of two cells or in the angle where 

 three or more liver cells meet, and it seems doubtful whether there is any delicate membrane 

 forming the wall of the channel. Heidenhain, however, thinks they have coats. The channels 



FIG. 1077. X-ray picture of the bile ducts and the pancreatic ducts. (Robinson.) 



thus formed radiate to the circumference of the lobule, and empty into small interlobular ducts 

 between the lobules! These are lined by low epithelial cells supported by a basement mem- 

 brane and a little fibrous tissue. The interlobular ducts pass into the portal canals, become 

 enclosed in Glisson's capsule, and, accompanying the portal vein and hepatic artery (Fig. 1076), 

 join with other ducts to form two main trunks, the right and left branches of the hepatic duct, 

 which leave the liver at the transverse or portal fissure, and by their union form the hepatic 

 duct. The larger interlobular ducts possess some circularly arranged smooth muscle tissue, 

 while the main ducts possess three coats mucous, muscular, and fibrous. The mucous coat 

 consists of tall columnar epithelial cells, basement membrane, and tunica propria. The mus- 

 cular coat consists of smooth muscle tissue circularly arranged. The fibrous coat consists of 

 loose white fibrous tissue supporting the other coats. 



The lymphatics, in the substance of the liver (Fig. 569), commence in lymphatic spaces 

 around the capillaries of the lobules; they accompany the vessels of the interlobular plexus, often 

 enclosing and surrounding them. These unite and form larger vessels, which run in the portal 

 canals, enclosed in Glisson's capsule, and emerge at the portal fissure to be distributed in the 

 manner described. Other superficial lymphatics arise from the superficial lobules, pass under 

 the peritoneum, and form a close plexus, where this membrane covers the liver. The first- 

 named group of lymphatics gives origin to the deep collecting trunks, the second to the superficial 



