PHYSIOLOGICAL ANATOMY OF THE LIVER. 433 



vein, to form the so-called vaginal plexus. From these vessels, a few arterial branches 

 are given off which pass between the lobules. The hepatic artery cannot be followed 

 beyond the interlobular spaces. The terminal branches of the hepatic artery are not 

 directly connected with the radicles of the hepatic veins, but they empty into small 

 branches of the portal vein within the capsule of Glisson. 



FIG. 129. Lobules of the liver, interlobular vessels, and intralobular veins. (Sappey.) 



1, 1, 1 1, 3, 4, lobules ; 2, 2, 2, 2, intralobular veins, injected with white ; 5, 5, 5, 5, 5, interlobular vessels, filled with a 



dark injection. 



The hepatic duct follows the general course of the portal vein ; but its structure and 

 relations are so important and intricate that they will be described separately. 



Interlobular Vessels. Branches of the portal vein, coming from the terminal ramifi- 

 cations as the vessel branches within the capsule and from the branches in the walls of 

 the capsule, are distributed between the lobules, constituting the greatest part of the 

 so-called interlobular plexus. These are situated between the lobules and surround them ; 

 each vessel, however, giving off branches to two or three lobules, and never to one alone. 

 They do not anastomose, and consequently they are not in the form of a true plexus. The 

 diameter of these interlobular vessels varies from ysVfr to Tlhr f an inch. In this distribu- 

 tion, the blood-vessels are followed by branches of the duct, which are much less numer- 

 ous and smaller, measuring only -^^ of an inch ; and some, even, have been measured 

 that are not more than -g-^Vs of an inch in diameter. 



Lobular Vessels. In the interlobular plexus, the ramifications of the hepatic artery 

 are lost, and this can no longer be traced as a distinct vessel. One of the peculiarities 

 of its arrangement, as we have seen, is that the artery does not empty into the radicles 

 of the efferent vein but joins the portal vessels as they are about to be distributed in a 

 true capillary plexus in the substance of the lobules. In the lobules themselves, conse- 

 quently, we have only to study the arrangement of the portal plexus, with the mode of 

 origin of the hepatic veins and the relations of the hepatic duct. 



The arrangement of the lobular plexus of blood-vessels is very simple. From the 

 interlobular veins, a number of branches (eight to ten) are given off arid penetrate the 

 lobule. As the interlobular vessels are situated between different lobules, each one 

 sends branches into two and sometimes three of these lobules ; so that, as far as vascular 

 supply is concerned, these divisions of the liver are never absolutely distinct. 



After passing from the interlobular plexus icto the lobules, the vessels immediately 

 break up into a close net-work of capillaries, from ^TF to *sW of an inch in diameter, 

 which occupy the lobules with a true plexus. These vessels are very numerous ; and, 

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