472 



OF SECRETION AND EXCRETION. 



cumference of each lobule towards its centre (where their ultimate rami- 

 fications terminate in those of the intralobular or hepatic vein), is desig- 

 nated as the lobular venous plexus. The Hepatic Artery sends branches to 

 every part of the Liver, supplying the walls of the portal and hepatic veins, 

 and of the hepatic ducts, as well as Glisson's capsule. The principal dis- 

 tribution of its branches, however, is to the lobules; which they reach, in 

 the same manner with the portal vessels and biliary ducts, by spreading 

 themselves through the interlobular spaces. There they ramify upon the 

 interlobular ducts, and upon the capsular surface of the lobules, which they 

 then penetrate, terminating for the most part in the portal venous plexus, 

 though a very few small branches may be traced into the Hepatic plexus of 

 capillaries. The whole of the blood, therefore, of the Hepatic Artery passes 

 through the lobuli, and is subservient to the secretion of Bile. It now only 

 remains to describe the Hepatic Veins, the branches of which occupy the in- 

 terior of the lobules, and are termed miralobular veins (Fig. 167, 1, 1; Fig. 

 168). On making a transverse section of a lobule, it is seen that the central 



Fiu. 1G8. 



Section of a small portion of the Liver of a Rabbit, with the Hepatic or iatralobular veins injected. 



vessel is formed by the convergence of numerous minute venules, which 

 arise from the plexus upon the surface of the lobule. The intralobular 

 veins terminate in the larger trunks, which pass along the bases of the lob- 

 ules, collecting from them their venous blood ; these are called by Mr. Kier- 

 nau sublobular veins. The main trunk of the Hepatic Vein terminates in 

 the ascending Vena Cava. 



389. The Hepatic Duct forms, by its subdivision and ramification, an inter- 

 lobular plexus very like that of the portal vein ; the branches ramifying 

 upon the capsular surface of the lobules, and ultimately penetrating into 

 their interior. The trunk and larger branches of the biliary duct consist 

 of an internal mucous membrane and an external fibrous sheath. The 

 former is very vascular and is lined by tall columnar cells, the latter is be- 

 lieved by Heriug to contain smooth muscular fibres, arranged longitudi- 

 nally, and a few bloodvessels; Asp, however, believes the spindle-cells and 

 striated appearance relied upon by Hering, Heidenhain and others, as evi- 

 dence of muscular fibres, to be due to elongated nuclei and connective-tissue 

 fibres, as they swell up and disappear in weak solution of hydrochloric acid 

 and alcohol. At the point where the interlobular ducts become continuous 

 with the network within the lobules, their diameter is very small, not ex- 

 ceeding ^ooth to -^Qgth of an inch; and here the epithelium, which in. 



