PHYSIOLOGICAL ANATOMY OF THE LIVER. 235 



to the hepatic veins, which are closely adherent to the sub- 

 stance of the liver, and remain open when they are cut 

 across. This sheath is prolonged over the vessels as they 

 branch and follows them in their subdivisions. It varies 

 considerably in thickness in different animals. In man and 

 the mammalia generally, it is rather thin, becoming more 

 and more delicate as the vessels subdivide, and is entirely 

 lost before the vessels are distributed in the interlobular 

 spaces. 



The vessels distributed in, and coming from the liver are 

 the following : 



1. The portal vein, the hepatic artery, and the hepatic 

 duct, passing in at the transverse fissure, to be distributed 

 in the lobules. The blood-vessels are continuous in the lob- 

 ules with the radicles of the hepatic veins. The duct is to 

 be followed to its branches of origin in the lobules. 



2. The hepatic veins ; vessels that originate in the lo- 

 bules, and collect the blood distributed in their substance by 

 branches of the portal vein and hepatic artery. 



Branches of the Portal Yein, the Hepatic Artery and 

 Duct. These vessels follow out the branches of the capsule 

 of Glisson, become smaller and smaller, and finally pass 

 directly between the lobules. In their course, however, 

 they send off lateral branches to the sheath ; and those who 

 follow exactly the description of Kiernan, call this the vagi- 

 nal plexus. The arrangement of the vessels in the sheath is 

 not in the form of a true anastomosing plexus, although 

 branches pass from this so-called vaginal plexus between the 

 lobules. These vessels, according to Sappey, do not anasto- 

 mose or communicate with each other in the sheath. 1 



The portal vein does not present any important pecu- 

 liarity in its course from the transverse fissure to the inter- 

 lobular spaces. It subdivides, enclosed in its sheath, until 

 its small branches go directly between the lobules, and in 



1 SAPPEY, Traite cT anatomic descriptive, Paris, 1857, p. 288. 



