STRUCTURAL ANATOMY OF THE LIVER. 583 



They proceed from before backwards, and terminate by two large 

 openings, corresponding to the right and left lobe of the liver in the 

 inferior vena cava. 



Summary. The liver has been shown to be composed of lobules; 

 the lobules (excepting at their bases ) are invested and connected to- 

 gether, the vessels supported, and the whole organ enclosed by Gils- 

 son's capsule; and they are so arranged, that the base of every lobule 

 in the liver is in contact with an hepatic vein (sublobular). 



The Portal vein distributes its numberless branches through portal 

 canals, which are channeled through every part of the organ ; it brings 

 the returning blood from the chylopoietic viscera ; it collects also the 

 venous blood from the ultimate ramifications of the hepatic artery in 

 the liver itself. It gives off branches in the canals, which are called 

 vaginal, and form a venous vaginal plexus; these give off interlobular 

 branches, and the latter enter the lobules and form lobular venous 

 plexuses, from the blood circulating in which the bile is secreted. 



The Bile in the lobule is received by a network of minute ducts, 

 the lobular biliary plexus; it is conveyed from the lobule into the 

 interlobular ducts ; it is thence poured into the biliary vaginal plexus 

 of the portal canals, and thence into the excreting ducts, by which it 

 is carried to the duodenum and gall-bladder, after being mingled in its 

 course with the mucous secretion from the numberless muciparous 

 follicles in the walls of the ducts. 



The Hepatic artery distributes branches through every portal canal ; 

 gives off vaginal branches which form a vaginal hepatic plexus, from 

 which the interlobular branches arise, and these latter terminate 

 ultimately in the lobular venous plexuses of the portal vein. The 

 artery ramifies abundantly in the coats of the hepatic ducts, enabling 

 them to provide their mucous secretion ; and supplies the vasa vaso- 

 rum of the portal and hepatic veins, and the nutrient vessels of the 

 entire organ. 



The Hepatic veins commence in the centre of each lobule by minute 

 radicles, which collect the impure blood from the lobular venous plexus 

 and convey it into the intralobular veins; these open into the sub- 

 lobular veins, and the sublobular veins unite to form the large hepatic 

 trunks by which the blood is conveyed into the vena cava. 



Physiological and pathological deductions. The physiological deduc- 

 tion arising out of this anatomical arrangement is, that the bile is 

 wholly secreted from venous blood, and not from a mixed venous and ar- 

 terial blood, as is stated by M tiller ; for although the portal vein re- 

 ceives its blood from two sources, viz., from the chylopoietic viscera 

 and from the capillaries of the hepatic artery, yet the very fact of the 

 blood of the latter vessel having passed through its capillaries into the 

 portal vein, or in extremely small quantity into the capillary network 

 of the lobular venous plexus, is sufficient to establish its venous 

 character.* 



* For arguments on this contested question, see the article " Liver," in the 

 " Cyclopaedia of Anatomy and Physiology," edited by Dr. Todd. 



