680 



ORGANS OF DIGESTION. 



from the liver the superfluous blood ; and the bile duct carries from the liver the 

 bile secreted by the hepatic cells. 



The hepatic cells form the chief mass of each lobule : they are of a more or 

 less spheroidal form ; but may be rounded, flattened, or many-sided, from mutual 

 compression. They vary in size from the j^Wth to the 30 '(j C th of an inch in 

 diameter, and contain a distinct nucleus in the interior, or even sometimes two. 

 In the nucleus is a highly refracting nucleolus, with granules. The cell-contents 

 are viscid, and contain yellow particles, the coloring matter of the bile, -ind oil 

 globules. The cells adhere together by their surfaces, so as to form rows, which 

 radiate from the centre towards the circumference of the lobule. These cells are 

 probably the chief agents in the secretion of the bile. 



Biliary ducts. The precise mode of origin of the biliary ducts is uncertain. 

 Mr. Kiernan's original view, confirmed as it is by the researches of Dr. Beale, 

 shows that the ducts commence within the lobules, in a plexiform network 

 (lobular biliary plexus), in which the hepatic cells lie. According to Henle, 

 Handfield Jones, and Kolliker, the cells are packed in the interspaces of the 

 capillary plexus, and, by means of temporary communications, transmit their 

 contents into the minute bile ducts which originate in the spaces between the 

 lobules, never entering within them. The ducts form a plexus (interlobular) 

 between the lobules ; and the interlobular branches unite into vaginal branches, 

 which lie in the portal canals, with branches of the portal vein and hepatic duct. 

 The ducts finally join into two large trunks which leave the liver at the trans- 

 verse fissure, and these joining form the hepatic duct. 



The Portal vein, on entering the liver at the transverse fissure, divides into 

 primary branches, which are contained in the portal canals, together with branches 

 of the hepatic artery and duct, and the nerves and lymphatics. In the larger 

 portal canals, the vessels are separated from the parietes, and joined to each other 

 by a loose cellular web, the capsule of Glisson. The veins, as they lie in the portal 

 canals, give off vaginal branches, which form a plexus (vaginal plexus) in 

 Glisson's capsule. From this plexus, and from the portal vein itself, small 

 branches are given off, which pass between the lobules (interlobular veins) ; these 

 cover the entire surface of the lobules, excepting their bases. The lobular 

 branches are derived from the interlobular veins ; they penetrate into the lobule, 

 and form a capillary plexus within them. From this plexus the intralobular vein 

 arises. 



The Hepatic artery appears destined chiefly for the nutrition of the coats of the 

 large vessels, the ducts, and the investing membranes of the liver. It enters 



the liver at the transverse fissure, with 

 the portal vein and hepatic duct, and 

 ramifies with these vessels through the 

 portal canals. It gives off vaginal branches, 

 which ramify in the capsule of Glisson ; 

 and other branches, which are distributed 

 to the coats of the vena portse and hepatic 

 duct. From the vaginal plexus, inter- 

 lobular branches are given off, which 

 ramify through the interlobular fissures, 

 a few branches being distributed to the 

 lobules. Kiernan supposes, that the 

 branches of the hepatic artery terminate 

 in a capillary plexus, which communicates 

 with the branches of the vena porta3. 



The Hepatic veins commence in the 

 interior of each lobule by a plexus, the 

 branches of which converge to form the 

 intralobular vein. 



The intralobular vein passes through the centre of the lobule, and leaves it at 

 its base to terminate in a sublobular vein. 



A transverse section of a small portal canal and its 

 vessels, after Kiernan. 1. Portal veiu ; 2, intrr- 

 lobular branches ; 3, branches ot'the vein, termed, 

 by Mr. Kiernan, vaginal, also giving off inter- 

 lobular branches ; 4, hepatic duct ; 6, hepatic 

 artery. 



