In the centre of each lobule is situated an intralobular vein (fig. 34, 5,) which is formed by the convergence of from " four to six or eight" minute venules, from the processes upon the surface of the lobule. In the super ficial lobules, the intralobular vein commences directly from the surface, and the minute ve nules by which it is formed may be seen in an ordinary injection converging from the circum ference towards the centre. The vein then takes its course through the centre of the longi tudinal axis of the lobule, and piercing the middle of its base opens into the sublobular vein. The intralobular veins have no direct communication with the portal vein or with the hepatic artery, and they simply serve to collect the blood which has circulated through the lobular venous plexus, and convey it into the general current of the hepatic veins. ' The sublobular veins (fig. 34) are named from their position at the base of the lobules. They are lodged in canals which are formed by the bases of all the lobules of the liver. They are extremely thin and "delicate in texture," and lie in close contact with the substance of the lobules, so that upon laying open one of these veins, the bases of the lobules may be seen distinctly through its coats. In the centre of the base of each of the lobules will be ob served the opening of the intralobular vein, so that the whole internal surface of the vein is pierced by these minute openings. In the smaller portal veins, on the other hand, where a number of small foramina were seen upon the' internal surface of that side of the vessel which lay in contact with the canal, and where the outline of the lobules was also perceptible, it was observed that the small openings cor responded with the interlobular spaces, and were the entrances of the interlobular veins.
The hepatic trunks receiving the blood from the sublobular veins take their course along the "hepatic venous canals," and—terminate by two large openings corresponding with the right and left lobes in the inferior cava, at the point where that vessel is lying deeply im bedded in the posterior border of the liver. A number of minor hepatic veins also terminate in the cava at this part of its course. The he patic venous canals resemble the portal canals in being formed by the capsular surfaces of the lobules, lined by a prolongation of the proper capsule. The hepatic trunks are thick and dense in their structure, and their external coat is composed of "longitudinal bands." From the thickness of their texture the outline of the lobules is not apparent through their coats, nor have they any intralobular veins opening into them.
The coats of the hepatic veins are supplied with blood by the hepatic artery, and the venous blood is returned to the ramifications of the portal vein.
The lymphatic vessels of the liver are divi sible into the deep and superficial. The former take their course through the portal canals, and through the right border of the lesser omentum, to the lymphatic glands situate in the course of the hepatic artery, and along the lesser curve of the stomach. They are easily injected (by
rupture of course) from the hepatic ducts, and Kiernan remarks, that " injection sometimes passes from the arteries and portal veins into the lymphatics. I have frequently seen them in the right border of the lesser omentum, when distended with injection, as large as small veins. The superficial lymphatics, (jigs. 32 and 33,) are situated in the cellular structure of the proper capsule, over the whole surface of the liver. Those of the convex surface are divided into two sets; 1st, those which pass from be fore backwards ; and 2d, those which advance from behind forwards. The former unite to form trunks, which enter between the folds of the lateral ligaments at the right and left extre mities of the organ, and of the coronary liga ment in the middle. Some of them pierce the diaphragm, and join the posterior mediastinal glands ; others converge to the lymphatic glands situated around the inferior cava. Those which pass from behind forwards consist of two groups; one ascends between the folds of the broad ligament, and perforates the diaphragm to terminate in the anterior mediastinal glands ; the other Curves around the anterior margin of the liver to its concave surface, and from thence to the glands in the right border of the lesser omentum. The lymphatic vessels of the con cave surface are variously distributed according to their position ; those from the right lobe terminate in the lumbar glands;—those from the gall-bladdcr, which are large and form a remarkable plexus, enter the glands in the right border of the lesser omentum ; and those from the left lobe converge to the lymphatic glands situated along the lesser curve of the stomach.
The nerves which supply the liver are de rived from the systems both of animal and organic life ; the former are filaments of the right phrenic and two pneumo-gastric nerves, and the latter of the solar plexus. The branches from the right phrenic nerve descend by the side of the inferior cava, to unite with the hepatic plexus in the right border of the lesser omen turn. Swan describes a small ganglion, to which filaments converge from the right semi lunar ganglion and right phrenic nerve, as being the medium of communication between the phrenic nerve and the hepatic plexus. The branches of the pneumo-gastric nerves pass between the two layers of the lesser omentum to its right border, and pursuing the course of the hepatic artery are distributed with the hepatic plexus to the gall-bladder and along the portal canals. The hepatic plexus proceeds from the solar plexus and surrounds the hepatic artery to the transverse fissure ; its filaments then accompany the branches of that vessel to their ultimate termination, and some few are observed to ramify upon the portal vein.