130 SPECIAL HISTOLOGY. 



middle, so that they are always about half the diameter of the 

 lobules distant from the nearest interlobular veins of the 

 vena porta. 



The hepatic artery, for the most part, accompanies the 

 portal vein and the biliary canals, is inclosed with the latter 

 in Glisson's capsule, and, in its principal ramifications, presents 

 precisely the same relations as the portal vein. It is finally 

 distributed upon the vessels and biliary ducts, in Glisson's 

 capsule, in the fibrous and serous coats of the liver, and in the 

 hepatic islets, whence its branches are denominated rami vas- 

 culares, capsulares, and lobulares. 



1. Rami vasculares. — As it divides, in company with the 

 vena porta, the hepatic artery gives off numerous small branches, 

 almost at right angles, which form a plexus in Glisson's cap- 

 sule, from which some lobular branches for the parietes of the 

 portal canal arise, on the side opposite to the arterial trunks ; 

 while many twigs proceed to the walls of the portal vein, the 

 larger branches of the artery itself, the hepatic veins, Glisson's 

 capsule and the biliary ducts. The distribution of the vessels 

 is particularly remarkable in the latter canals, so that, in a good 

 injection, they appear almost as red as the arteries themselves. 



A moderately close capillary network exists around all these 

 parts, even the glands of the biliary ducts, whence the venae 

 vasculares arise and open, as Ferrein discovered and as all 

 the moderns since Kiernan have agreed, not into the hepatic 

 vein, but into small portal twigs, as these are leaving the 

 larger branches in Glisson's capsule, and are therefore to be 

 regarded as internal, or hepatic radicles of the portal vein. 

 From this cause the portal vein may be partially injected from 

 the hepatic artery and conversely. Again, in injecting the he- 

 patic artery and the portal vein, the vascular network in ques- 

 tion may be filled from both sides ; while it is not possible 

 directly to force injection from the hepatic vein into them. 



2. Rami capsulares. — Independently of a few branches 

 given off by the artery, before its entrance into the liver, to the 

 fossa ductus venosi, to the ligamentum teres and suspensorium, 

 all the arterial twigs of the coats of the liver are the terminal 

 prolongations of certain arteries which penetrate the liver and 

 appear in different parts of its surface between the hepatic 

 islets. At the points of exit, and even before reaching them, 



