THE LIVER. 541 



1G2. Vessels and nerves of the liver. The arrangement of the blood- 

 vessels in the liver distinguishes it from all other organs, inasmuch as, 

 besides an artery and an efferent vein, it possesses an additional, 

 afferent vein, the vena portce. While the latter is appropriated to the 

 supply of the secreting parenchyma, being directly continuous through 

 the capillary network with the hepatic vein, the artery is more espe- 

 cially distributed to the walls of the biliary ducts and of the portal vein, 

 to Glisson's capsule, and to the serous investment of the liver, taking 

 only a subordinate share in supplying the capillary network of the 

 hepatic islets. The ramifications of the portal vein, and of a few small 

 veins of the stomach and gall bladder (see Weber, Ann. Acad. 1845), 

 which enter the liver independently, take place for the most part dichoto- 

 mously ; but both larger and smaller branches, besides the main trunk, 

 into which they divide, give off a number of small vessels at right angles. 

 The latter, often after a very short course, at once enter the hepatic 

 islets contiguous to the largest vascular canals, while the larger portal 

 branches, ramifying continually, and becoming finer and finer, have, 

 according to their diameter, to take a longer or a shorter course through 

 the hepatic parenchyma in the canals lined by the capsule of Glisson, 

 before they enter the hepatic islets or lobules. Each of these receives, 



and closed extremities, which have nearly the same diameter, as the duct itself; others seem 

 to lose their tubular character, their nuclei becomes less closely set together, and the uniting 

 substance more faintly granular and indefinite; the duct, in short, gradually ceases, losing 

 all determinate structure. In some, of rather minute size, -3^$^ sVjjijth f an i ncn i n dia- 

 meter, the exterior form remains distinct, but the canal is almost obliterated by the close ap- 

 proximation of the nuclei of the opposite walls. These structures now described, I believe 

 to be truly the terminal branches of the hepatic duct, from which they certainly originate. 

 They seem gradually to lay aside the several component tissues of the larger ducts, the 

 fibrous coat blending with the ramifications of Glisson's capsule, the basement membrane 

 imperceptibly ceasing, and the epithelium becoming resolved at last into its simple funda- 

 mental nuclei" (I. c., p. 125). 



It is important to remark, that in a Dog, Dr. H. Jones found biliary matter in the interlo- 

 bular fissures. 



From the fact that in the contents of the hepatic ducts of Man and the Sheep, extracted by 

 means of a forceps and without injuring the organ, hepatic cells may be detected, Mr. Whar- 

 ton Jones (" Phil. Trans.," 1848) draws the conclusion that the hepatic cells are endogenous 

 cells, answering to the epithelium of other glands which was Henle's view. It is impossi- 

 ble to doubt a fact stated by so careful an observer ; but, however these cells may have got 

 into the large biliary ducts, it is quite clear, from a comparison of diameters, that they can- 

 not enter the minutest ones the total diameter of the latter being the same as that of the 

 cells, viz. T ^ ffff th of an inch. 



We are strongly inclined to believe that the view taken by Dr. H. Jones is in the main \ 

 correct that the liver is essentially of the same order as the " ductless" glands, and should \ 

 be placed in the same category as the Peyerian follicles, spleen, &c. In fact, startling as this 

 view may at first appear, a very clear transition between the Peyerian follicles, &c., and the 

 liver, is afforded by the tonsils ; which, on the one hand, are identical with Peyer's follicles, 

 in sc far as they are solid vascular networks, whose meshes are filled by a morphologically 

 indifferent tissue ; while, on the other hand, without differing from the liver in this respect 

 \ they resemble it in having these elements arranged around diverticula of the intestinal 

 \ mucous membrane. TBS.] 



