940 THE ORGANS OF DIGESTION. 



The hepatic artery, entering the liver at the transverse fissure with the portal 

 vein and hepatic duct, ramifies with these vessels through the portal canals. It 

 gives off vaginal branches which ramify in the capsule of Glisson, and appear to 

 be destined chiefly for the nutrition of the coats of the large vessels, the ducts, 

 and the investing membranes of the liver. It also gives off capsular branches 

 which reach the surface of the organ, terminating in its fibrous coat in stellate 

 plexuses. Finally it gives off interlobular branches which form a plexus on the 

 outer side of each lobule, to supply its wall and the accompanying bile-ducts. 

 From this, lobular branches enter the lobule and end in the capillary network 

 between the cells. Some anatomists, however, doubt whether it transmits any 

 blood directly to the capillary network. 



The portal vein also enters at the transverse fissure and runs through the 

 portal canals, enclosed in Glisson's capsule, dividing into branches in its course, 

 which finally break up into a plexus (the interlobular plexus] in the interlobular 

 spaces. In their course these branches receive the vaginal and capsular veins, 

 corresponding to the vaginal and capsular branches of the hepatic artery (Fig. 515). 

 Thus it will be seen that all the blood carried to the liver by the portal vein and 

 hepatic artery, except perhaps that derived from the interlobular branches of the 

 hepatic artery, directly or indirectly finds its way into the interlobular plexus. 

 From this plexus the blood is carried into the lobule by fine branches which pierce 

 its wall and then converge from the circumference to the centre of the lobule, 

 forming a number of converging vessels which are connected by transverse branches 

 (Fig. 516). In the interstices of the network of vessels thus formed are situated, 



Trunk of intralobular 

 vein. 



Intralobular vein. 



FIG. 516. Horizontal section of liver (dog). 



as before said, the liver-cells : and here it is that, the blood being brought into 

 intimate connection with the liver-cells, the bile is secreted. Arrived at the centre 

 of the lobule, all these minute vessels empty themselves into one vein, of consider- 

 able size, which runs down the centre of the lobules from apex to base and is called 

 the intralobular vein. At the base of the lobule this vein opens directly into the 

 sublobular vein, with which the lobule is connected, and which, as before men- 

 tioned, is a radicle of the hepatic vein. The sublobular veins, uniting into larger 

 and larger trunks, end at last in the hepatic veins, which do not receive any intra- 

 lobular veins. Finally, the hepatic veins, as mentioned at page 619, converge to 

 form three large trunks which open into the inferior vena cava, while that vessel 

 is situated in the fissure appropriated to it at the back of the liver. 



(3) The Ducts. Having shown how the blood is brought into intimate relation 

 with the hepatic cells in order that the bile may be secreted, it remains now only 

 to consider the way in which the secretion, having been formed, is carried away. 



