THE LIVER. 543 



the interval between them. The meshes of the network correspond, of 

 course, in form, with the hepatic cell-network, and are thence more elon- 

 gated in the interior of the hepatic islets, more rounded externally, 

 ■whilst their breadth corresponds with that of the columns of the hepatic 

 cells, being about O-OOG-0-02 of aline. 



The hepatic veins essentially resemble the portal vein, in so far as 

 they possess no valves, branch out at acute angles and do not anasto- 

 mose ; their larger branches also receive numerous minute vessels, but 

 these lie isolated in special canals in the hepatic substance to which they 

 are firmly attached, whence they do not collapse when cut across, and, 

 at least in their finer ramifications, possess no external investment of 

 connective tissue, which is indeed but very rudimentary, even in the 

 largest trunks. The relations of the ultimate branches of the hepatic 

 vein, termed by Kiernan intra-lobular veins, and by Krukenberg, venoe 

 centrales lobulorum, are, however, totally different from those of the 

 portal ramuscules. These veins, which in Man are 0"012-0'03 of a line 

 in diameter, are best studied in some animal whose liver breaks up into 

 isolated lobules, as the Pig; after which Kiernan has given his some- 

 what diagrammatic figure. If we here open a small branch of the 

 hepatic vein, polygonal arere are descried through the walls of the ves- 

 sel — the outlines of those surfaces of the lobules which are turned towards 

 the vein (Fig. 218). 



A minute vein which, in the centre of each of these surfaces, termed 

 by Kiernan "bases of the lobules," opens directly into the larger vessel 

 leads, if we trace it in the opposite direction, into the interior of a lobule, 

 where it arises from the capillary network ; but under no circumstances 

 is it continued into a second or third lobule. In this way only a single 

 vein, which may thence be called vena intralobularis, arises in each 

 lobule. The vessels into which these veins directly open are called by 

 Kiernan sublobidares, because they run along the basal surfaces of the 

 lobules. They are sometimes large, attaining as much as 1-2 lines in 

 the Pig, and then lie in canals which are surrounded by the basal sur- 

 faces of a certain number of lobules ; at other times they are smaller, 

 down to 1-30 of a line, in which case they only pass between the lobules. 

 The sublobular veins unite into larger veins, which continue to receive, 

 directly, but few or no other intralobular veins, and thence, are only 

 partly or not at all bounded by the basal surfaces of the lobules, but 

 only by their lateral or apical surfaces ("capsular surfaces," Kiernan). 

 Such veins, when they are smaller, still receive sublobular veins from 

 the groups of lobules which immediately surround them ; or, lastly, only 

 larirer veins, which have the same relations as themselves. 



The intralobular veins are very simply arranged. Each of them 

 penetrates directly into the axis of an hepatic islet, or lobule, dividing 

 in the middle into two or three principal branches, which frequently 



