STRUCTURE OF LIVER IN THE OX. 115 



and closely packed, held together jointly by a fine areolar tis- 

 sue, and the blood-vessels and ducts concerned in their peculiar 

 office. These lobules are believed to be isolated that is, each 

 to be independent of connection with the others. Their union 

 with the minute blood-vessels is very remarkable. The blood- 

 vessels of the liver are the hepatic artery, a branch of the C03liac 

 axis, derived in. turn from the posterior aorta ; the portal vein, 

 which, formed from the veins of all the organs concerned in 

 digestion, is distributed like an artery within the liver; and the 

 hepatic veins, which, receiving all the blood that enters the 

 liver, return it to the vena cava in the abdomen. 



Each lobule of the liver rests with its base on a minute twig 

 of the hepatic venous system ; a still more minute twig de- 

 scends from the centre of the lobule to join the twig at its 

 base ; the twig which descends to the base of the lobule is 

 formed by the union of the capillary blood-vessels contained in 

 the lobule. The hepatic venous system, in its course from the 

 liver, does not run side by side with the branches of the 

 hepatic artery, but reaches the hepatic venous trunks by chan- 

 nels peculiar to itself. On the contrary, the hepatic artery, the 

 portal vein, and the hepatic duct, and their subdivisions, enter 

 the liver together, and, having a parallel distribution, pursue 

 their course through ramified common passages termed portal 

 canals. It is these vessels which are accompanied by the cap- 

 sule of Glisson in their course through the portal canals. The 

 minute branches of the portal vein pass into the substance of 

 each lobule. The minute branches of the hepatic artery also 

 pass into each lobule, supplying the accompanying ducts in 

 particular with blood. It is believed, further, that the capil- 

 laries supplied with blood by the hepatic artery throw their 

 blood, now become venous, into the terminal branches of the 

 portal system ; and that the secretion of bile in each lobule is 

 the product of the venous blood drawn by the general portal 



