746 



ORGANS OF DIGESTION". 



Fig. 411. 



cumference. s The radicals of the portal vein communicate with those of the 

 hepatic vein, which occupy the centre of the lobule; and the latter converge 

 to form the intralobular vein, which issues from the base of the lobule, and 

 joins the hepatic vein. The portal vein carries the blood to the liver, from 

 which the bile is secreted ; the hepatic vein carries the superfluous blood from 

 the liver, and the bile-duct carries the bile secreted by the hepatic cells. 



The hepatic cells 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 T7 )Vff to the ^Va f an i n h i n diameter, and contain a distinct nucleus in 

 the interior, or 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, and oil globules. The cells adhere together by their 

 surfaces, so as to form rows, which radiate from the centre towards the circum- 

 ference of the lobule. These cells are probably the chief agents in the secre- 

 tion of the bile. 



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

 Mr. Kiernan's original view, which is supported by the researches of Dr. Beale, 

 is 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 and form vaginal branches, 

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



The ducts finally form two large trunks, which 

 leave the liver at the transverse fissure, and 

 the union of these is 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, to- 

 gether 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 (va- 

 ginal plexus) in Glisson's capsule. From this 

 plexus, and from the portal vein itself, small 

 branches are given off, which pass between thfe 

 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 porta3 and hepatic duct. From the 

 vaginal plexus, interlobular 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. 



A transverse section of a small portal 

 canal and its vessels, after Kiernan. 1. 

 Portal vein ; 2, interlobular branches ; 

 3, branches of the vein, termed, by Mr. 

 Kiernan, vaginal, also giving off inter- 

 lobular branches ; 4, hepatic duct ; 5, 

 hepatic artery. 



