516 



OF SECRETION. 



Horizontal section of two superficial Lobules, showing 

 the interlobular plexus of biliary ducts; 1, 1, intralobular 

 veins; 2, 2, trunks of biliary ducts, proceeding from the 

 plexus which traverses the lobules ; 3, interlobular tissue ; 

 4, parenchyma of the lobules. (After Kiernan.) 



initiations of these ducts have not, however, been traced in the adult Liver of any of the 

 higher animals, although they are sufficiently evident in the embryonic condition. From 

 the analogy of other organs, there would seem good reason to believe, that the ultimate 



ramifications of the hepatic ducts an- 



Fig 141. astomose freely together, and that 



they form a net-work, in which their 

 terminations are lost, as it were, with- 

 out forming true caeca.* This view of 

 the matter finds confirmation in the 

 curious fact pointed out by Mr. Kier- 

 nan, that, in the left lateral ligament, 

 the essential parts of a lobe are found 

 in the simplest form and arrangement. 

 From the edge of the liver next to the 

 ligament, numerous Ducts emerge, 

 which ramify between the two layers 

 of peritoneum of which the ligament 

 is composed. They are accompanied 

 by branches of the Portal and Hepatic 

 Veins, and of the Hepatic Artery; 

 which also ramify in this ligament, 

 especially around' the parietes of the 

 ducts. These ducts, of which some 

 are occasionally of considerable size, 

 divide, subdivide, and anastomose 

 with each other; and the meshes 



formed by the network of larger or excreting Ducts, are occupied by minute plexuses 

 of their ultimate ramifications or secreting Ducts. 



d. The Hepatic Artery sends branches to every part of the Liver, supplying the walls 

 of the Portal and Hepatic Veins, and of the Hepatic Ducts, as well as Glisson's capsule. 

 The principal distribution of its branches, however, is to the Lobules, which they reach 

 in the same manner with the Portal vessels and Biliary Ducts, by spreading themselves 

 through the interlobular spaces. There they ramify upon the interlobular ducts, and 

 upon the capsular surface of the lobules, which they then penetrate; their minuteness 

 prevents their distribution within the lobules from being clearly demonstrable; but, as 

 they enter along with the biliary ducts, there can be little doubt that, here as elsewhere, 

 they are principally distributed upon the walls of these. As to the ultimate termination 

 of the capillaries of the Hepatic Artery, whether they enter the Portal plexus or the 

 Hepatic Vein, there is a difference of opinion amongst anatomists; the former view 

 being upheld by Kiernan, the latter by Mullen The question is a very interesting one 

 in a physiological point of view; since if the former account be the true one, the Blood 

 which is brought to the Liver by the Hepatic Artery becomes subservient to the secretion 

 of Bile, only by passing into the Portal plexus; whilst, if the latter be the correct state- 

 ment, either the arterial Blood is not at all subservient to the formation of Bile, or the 

 secretion can be elaborated from the arterial capillaries. The experiments of Mr. Kier- 

 nan have satisfactorily proved, that the Intra-lobular or Hepatic Veins cannot be filled 

 by injection from the Hepatic Artery, though they may be readily filled from the Portal 

 plexus; whilst, on the other hand, there is reason to believe that a very fine injection 

 into the Hepatic arteries will find its way into the Portal plexus.f It is certain that all 

 the branches of the Hepatic artery, of which the termination can be ascertained, end in 

 the Vena portae; a free capillary communication existing between their two systems of 

 branches, on the walls of the larger blood-vessels and ducts. According to Muller, there 

 is an ultimate plexus of capillary vessels, with which all the three systems freely com- 

 municate ; but for this idea there is no adequate foundation ; and it is inconsistent with 

 the fact just stated, that injection into the Hepatic Artery does not return by the Hepatic 

 vein. And the views of Mr. Kiernan have lately received important confirmation from 

 the researches of Mr. Bowman on the circulation in the Kidney ( 667, 6). 



e. It now only remains to describe the Hepatic Veins, the branches of which occupy 

 the interior of the Lobules, and are termed intra-lobular veins (1, 1, Fig^s. 140 and 141). 

 On making a transverse section of a Lobule, it is seen that the central vessel is formed 

 by the convergence of from four to six or eight minute venules, which arise from the 

 processes upon the surface of the lobule. In the superficial lobules (by which term are 



* See Wilson in Cyclopaedia of Anatomy and Physiology, vol. iii., p. 170. 

 -[This is stated to have been the case in the injections of Lieberkuhn, although Mr. 

 Kiernan has not succeeded in effecting it. 



