356 USES OF THE LIVER DUCTLP;SS GLANDS 



be more fully described in connection with the arrangement and dis- 

 tribution of the hepatic vessels. 



The substance of the liver is made up of lobules of an irregularly- 

 ovoid or rounded form and about ^ of an inch ( I millimeter) in diameter. 

 The space which separates these lobules is about one-quarter of the 

 diameter of the lobule and is occupied by the bloodvessels, nerves and 

 ramifications of the hepatic duct. In certain animals, the pig and the 

 polar bear, the division of the hepatic substance can readily be made 

 out with the naked eye ; but in man and in most of the mammalia, the 

 lobules are not so distinct, although their arrangement is essentially 

 the same. The lobules are intimately connected with each other, and 

 branches going to a number of different lobules are given off from the 

 same interlobular vessels ; but they are sufficiently distinct to represent, 

 each one, the general anatomy of the secreting portion. 



At the transverse fissure, the portal vein, having collected the blood 

 from the abdominal organs, and the hepatic artery, which is a branch of 

 the cceliac axis, penetrate the substance of the liver, with the hepatic 

 duct, nerves and lymphatics, all enveloped in the fibrous vagina, or 

 sheath. The portal vein is by far the larger of the two bloodvessels ; 

 and its calibre may be roughly estimated as eight to ten times that 

 of the artery. 



The vagina, or capsule of Glisson, is composed of fibrous tissue in 

 the form of a dense membrane, closely adherent to the adjacent struc- 

 ture of the liver, and enveloping the vessels and nerves, to which it is 

 attached by loose areolar tissue. The attachment of the bloodvessels 

 to the sheath is so loose that the branches of the portal vein are col- 

 lapsed when not filled with blood ; presenting a striking contrast to the 

 hepatic veins, which are closely adherent to the substance 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 in 

 the mammalia generally, it is rather thin, becoming more and more 

 delicate as the vessels subdivide. It is lost before the vessels are dis- 

 tributed between the lobules. 



The vessels distributed in the liver are the following : 



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 lobules with the radicles of the hepatic 

 veins. The duct is to be followed to its branches of origin in the lobules., 



The hepatic veins ; vessels that originate in the lobules, and collect 

 the blood distributed in their substance by branches of the portal vein 

 and of the hepatic artery. 



