254 DIGESTION. 



liver, it will be well to trace, first, the two bloodvessels and 

 the duct which enter the organ on the under surface at the 

 transverse fissure, viz., the portal vein, hepatic artery, and he- 

 patic duct. As before remarked, all three run in company, 

 and their appearance on longitudinal section is shown in Fig. 

 85. Running together through the substance of the liver, 



FIG. 85. 



Longitudinal section of a portal canal, containing a portal vein, hepatic artery, 

 and hepatic duct, from the pig (after Kiernan) ^. p, branch of vena portse, situated 

 in a portal canal, formed amongst the lobules of the liver, and giving off vaginal 

 branches; there are also seen within the large portal vein numerous orifices of the 

 smallest interlobular veins arising directly from it ; A, hepatic artery ; D, hepatic 

 duct. 



they are contained in small channels, called portal canals, their 

 immediate investment being a sheath of areolar tissue, called 

 Glisson's capsule. 



To take the distribution of the portal vein first: In its course 

 through the liver this vessel gives off small branches, which 

 divide and subdivide between the lobules surrounding them 

 and limiting them, and from this circumstance called inter- 

 lobular veins; From these small vessels a dense capillary net- 

 work is prolonged into the substance of the lobule, and this 

 network gradually gathering itself up, so to speak, into larger 

 vessels, converges finally to a single small vein, occupying the 

 centre of the lobule, and hence called wJralobular. This ar- 



