PHYSIOLOGICAL ANATOMY OF THE LIVER. 



395 





called the intralobular vein. A single lobule, surrounded by an interlobular 

 vessel, showing the lobular capillary plexus, and the central vein (the intra- 

 lobular vein) cut across, 



i * VA # AM&. '* 



in 



Fig. 



FIG. 131. Transverse section of a single hepatic lobule (Sappey). 



intralobular vein, cut across ; 2, 2, 2, 2, afferent branches of the intra- 

 lobular vein ; 3, 3. 3, 3, 3, 3, 3, 3, 3, interlobular branches of the portal 

 vein, with its capillary branches, forming; the lobular plexus, ex- 

 tending to the radicles of the Lutralobular vein. 



is represented 

 131. 



Intralobular Veins. 

 The capillaries of 

 the lobules converge 

 into three or four ve- 

 nous radicles (2, 2, 2, 2, 

 in Fig. 131), which 

 empty into a central 

 vessel. This is the in- 

 tralobular vein. If a 

 liver be carefully in- 

 jected from the he- 

 patic veins, and if sec- 

 tions be made in vari- 

 ous directions, it will 

 be seen that the intra- 

 lobular veins follow the 

 long axis of the lobules, receiving vessels in their course, until they empty 

 into a larger vessel situated at what may be called the base of the lobules. 

 These latter are the sublobular veins. They collect the blood in the manner 

 just described, from all parts of the liver, unite with others, becoming larger 

 and larger, until finally they form the three hepatic veins, which discharge 

 the blood from the liver into the vena cava ascendens. 



The hepatic veins differ somewhat in their structure from other portions 

 of the venous system. Their walls are thinner than those of the portal veins, 

 they are not enclosed in a sheath, and they are very closely adherent to the 

 hepatic tissue It has also been noted that the hepatic veins possess a well 

 marked muscular tunic, very thin in man, but well developed in the pig, the 

 ox and the horse, and composed of non-striated muscular fibres interlacing 

 with each other in every direction. 



In addition to the blood-vessels just described, the liver receives venous 

 blood from vessels which have been called accessory portal veins, coming 

 from the gastro-hepatic omentum, the surface of the gall-bladder, the dia- 

 phragm and from the anterior abdominal walls. These vessels penetrate at 

 different points on the surface of the liver, and they may serve as deriva- 

 tives, when the circulation through the portal vein is obstructed. 



Structure of a Lobule of the Liver. Each hepatic lobule, bounded and 

 more or less distinctly separated from the others by the interlobular vessels, 

 contains blood-vessels, radicles of the hepatic ducts and the so-called hepatic 

 cells. The arrangement of the blood-vessels has just been described ; but 

 in all preparations made by artificial injection, the space occupied by the 

 blood-vessels is exaggerated by excessive distention, and the difficulties in 



