358 



USES OF THE LIVER DUCTLESS GLANDS 



sometimes three of these lobules; so that, so far as vascular supply 

 is concerned, the lobular divisions of the liver are never absolutely 

 distinct. 



After passing from the interlobular plexus into the lobules, the 

 vessels immediately break up into an elongated network of capillaries, 

 3Wo to 2 2 3 o"o f an * nc h (^ to ii ft) in diameter, which occupy the 

 lobules with a true plexus. These vessels are very abundant. The 

 blood, having been distributed in the lobules by this lobular plexus, is 

 collected by three or four venous radicles into a single central vessel 

 situated in the long axis of the lobule, called the intralobular vein. A 

 single lobule, surrounded by interlobular vessels, showing the lobular 

 capillary plexus, and the central vein (the intralobular vein) cut across, 



is represented in Fig. 75 

 and Plate VII, Fig. 5. 



Intralobular Veins. 

 The capillaries of the 

 lobules converge into 

 three or four venous 

 radicles (2, 2, 2, 2, in Fig. 

 75) which empty into a 

 central vessel. This is 

 the intralobular vein. If 

 a liver is carefully in- 

 jected from the hepatic 

 veins, and if sections 

 are made in various di- 

 rections, it will be seen 

 that the intralobular 



75- Transverse section of a single hepatic lobule (Sappey). 

 I, intralobular vein, cut across ; 2, 2, 2, 2, afferent branches of 



the intralobular vein ; 3, 3, 3, 3, 3, 3, 3, 3, 3, interlobular branches veins f ollow the long 

 of the portal vein, with its capillary branches, forming the lobular r f i 1 K 1 c r<=> 



plexus, extending to the radicles of the intralobular vein. es > r 



ceiving 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 

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

 not enclosed in a sheath and they are 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, 



