466 



LIVER. 



[CHAP, xxxiii. 



of the several twigs of the portal vein, hepatic artery, and duct, 

 may be said to be determined by the mode of distribution of 

 these vessels. The intralobular hepatic vein occupies the central 

 axis of the lobules, and usually consists of a stem, into which three 

 to five, or even more, subordinate twigs empty the blood derived 

 from the capillary plexus. The lobule is elongated on this vein, 

 and presents a process for each of the subordinate twigs. 



In all cases, the terminal branches of the portal vein and the 

 duct arrive at the surface of the lobule at several points ; and the 

 surface of the lobule, whether complete or incomplete, is continuous 

 with that of the portal canals. From this surface, in all cases, the 

 capillary plexus tends by the slight elongation of its close meshes 

 and converges towards the intralobular hepatic vein in the axis of 

 the lobule. It probably follows, that in this latter situation the 

 blood, after having been nearly deprived of those constituents from 

 which the bile is formed, circulates more rapidly than at the more 

 external parts of the lobule, whither it has just been brought by 

 the portal veins, richly charged with these constituents. 



Portal Canals. It has been already observed, that the portal 

 canals contain a branch of the portal vein with a branch of the 



hepatic artery, and of the bi- 



ft'p-220. liary duct not unfrequently 



the vein is accompanied by 

 two branches of the artery 

 and duct. 



The branches of the artery 

 and duct are connected with 

 those of the portal vein by are- 

 olar tissue, which is abundant 

 in the transverse fissure of the 

 liver, and in the larger portal 

 canals, but in the smaller 

 exists chiefly on that side of 

 the vein where the artery and 

 duct lie; while, as the vessels 

 diminish in size, the amount 

 of this areolar tissue becomes 

 less until it entirely ceases 

 where the small branches 

 lobules are 

 I given off. 

 g . Hepatic areolar tissuc ^ described under 



Longitudinal section of a small portal vein and canal 

 after Kiernan. a. Portions of the canal from which the 

 vein has been removed. 6. Side of the portal vein in 

 contact with the canal, c. The side of ths vein which is 

 separated from the canal by the hepatic artery and __T_- -L o,,^^!-, 

 duct with areolar tissue (Glisson's capsule), d. In- WlU Supply 



, This investment of 



veins. / Vaginal veins of Kiernan. 

 h. Hepatic duct. 



