LIVER. 77 



Distribution of Vessels. The portal vein and hepatic artery, upon 

 entering the liver, penetrate its substance, divide into smaller and smaller 

 branches, occupy the spaces between the lobules, completely surrounding 

 and limiting them, and constitute the interlobular vessels. The hepatic 

 artery, in its course, gives off branches to the walls of the portal vein and 

 Glisson's capsule, and finally empties into the small branches of the porta I 

 vein in the interlobular spaces. 



The interlobular vessels form a rich plexus around the lobules, from 

 which branches pass to neighboring lobules and enter their substance, 

 where they form a very fine network of capillary vessels, ramifying over 

 the hepatic cells, in which the various functions of the liver are performed. 

 The blood is then collected by small veins, converging toward the centre 

 of the lobule, to form the intralobular vein, which runs through its long 

 axis and empties into the sub-lobular vein. The hepatic veins are formed 

 by the union of the sub-lobular veins, and carry the blood to the ascending 

 vena cava; their walls are thin and adherent to the substance of the 

 hepatic tissue. 



The Hepatic Ducts or Bile Capillaries originate within the lobules, 

 in a very fine plexus lying between the hepatic cells ; whether the smallest 

 vessels have distinct membranous walls, or whether they originate in the 

 spaces between the cells by open orifices, has not been satisfactorily deter- 

 mined. 



The Bile Channels empty into the interlobular ducts, which measure 

 about ^Vo f an mc ^ m diameter, and are composed of a thin homogeneous 

 membrane lined by flattened epithelial cells. 



As the interlobular bile ducts unite to form larger trunks, they receive 

 an external coat of fibrous tissue, which strengthens their walls; they 

 finally unite to form one large duct, the hepatic duct, which joins the cystic 

 duct ; the union of the two forms the ductus communis choledochus, which 

 is about three inches in length, the size of a goose quill, and opens into 

 the duodenum. 



The Gall Bladder is a pear-shaped sack, about four inches in length, 

 situated in a fossa on the under surface of the liver. It is a reservoir for 

 the bile, and is capable of holding about one ounce and a half of fluid. It 

 is composed of three coats, (i) serous, a reflection of the peritoneum, (2) 

 fibrous and muscular, (3) mucous. 



(i) Bile. Mechanism of its Secretion. Bile does not preexist in 

 the blood, but is formed in the interior of the hepatic cells, from materials 

 derived from the venous as well as arterial blood. The secreted bile is 



