584 



OF SECRETION AND EXCRETION. 



Horizontal section of three superficial Lobules, 

 showing the two principal systems of Bloodvessels : 

 1, 1, mfralobular veins, proceeding from the Hepatic 

 veins ; 2, 2, interlobular plexus, formed by branches 

 of the Portal vein. 



duct are distributed, in the manner to be presently described. 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 inter- 

 Fig. 153. lobular 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 demonstra- 

 ble ; but, as they enter along with the 

 biliary ducts, there can be little doubt 

 that, here as elsewhere, they are prin- 

 cipally 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 differ- 

 ence of opinion amongst anatomists; the 

 former view being upheld by Kiernan, 

 the latter by Miiller. The question is 

 a very interesting one in a physiological 

 point of view; since, if the former ac- 

 count be the true one, the blood which 

 is brought to the liver by the hepatic 

 artery becomes subservient to the secre- 

 tion of bile, only by passing into the portal plexus; whilst, if the latter be the 

 correct statement, either the arterial blood is not at all subservient to the for- 

 mation of bile, or the secretion can be elaborated from the arterial capillaries. 

 The experiments of Mr. Kiernan have satisfactorily proved that the intralobu- 

 lar 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. 1 It is certain that all the branches of 

 the hepatic artery, of which the termination can be ascertained, end in the vena 

 portse; a free capillary communication existing between their two systems of 

 branches, on the walls of the larger bloodvessels and ducts. According to 

 Miiller, there is an ultimate plexus of capillary vessels, with which all the three 

 systems freely communicate; 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. The views of Mr. Kiernan upon this 

 point have received important confirmation from the researches of Mr. Bowman 

 on the circulation in the Kidney ( 635). It now only remains to describe the 

 Hepatic Veins, the branches of which occupy the interior of the lobules, and 

 are termed m^ralobular veins (1, 1, Figs. 153, 154). On making a transverse 

 section of a lobule, it is seen that the central vessel is formed by the converg- 

 ence 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 designated those lobules which lie upon the exterior of the glandular 

 substance, not only upon the surface of the liver, but also against the walls of the 



1 This is stated to have been the case in the injections of Lieberkiihn, although Mr. 

 Kiernan has not succeeded in effecting it. 



