THE LIVER. 



1059 



ing varicosities, and are distributed to the blood-vessels and ducts, and to spaces 

 between the liver-cells, and follow the biliary canaliculi (Berkeley). The phrenic 

 nerves supply part of the external surface of the liver. 



Structure. The substance of the liver is composed of lobules held together by 

 an extremely fine areolar tissue, and of the ramifications of the portal vein, hepatic 

 duct, hepatic artery, hepatic veins, lymphatics, and nerves, the whole being 

 invested by a serous and a fibrous coat. 



The serous coat is derived from the peritoneum, and invests the greater part 

 of the surface of the organ. It is intimately adherent to the fibrous coat. 



The fibrous coat lies beneath the serous investment and covers the entire sur- 

 face of the organ. It is difficult of demonstration, excepting where the serous 

 coat is deficient. At the transverse fissure it is continuous with the capsule of 

 Glisson, and on the surface of the organ with the areolar tissue separating the 

 lobules. 



The lobules form the chief mass of the hepatic substance ; they may be seen 

 either on the surface of the organ or by making a section through the gland. 



Hepatic 



artery. 



Portal vein. 



Orifices of intralobular veins. 



FIG. 669. Longitudinal section of an hepatic 

 vein. (.After Kiernan.) 



Portion of 

 canal from 

 which vein 

 has been 

 removed. 



FIG. 670. Longitudinal section of a small portal 

 vein and canal. (After Kiernan.; 



They are small granular bodies about the size of a millet-seed, measuring from 

 one-twentieth to one-tenth of an inch in diameter. In the human subject their 

 outline is very irregular, but in some of the lower animals (for example, the pig) 

 they are well-defined, and when divided transversely have a polygonal outline. 

 If divided longitudinally they are more or less foliated or oblong. The bases of 

 the lobules are clustered round the smallest radicles (sublobular) of the hepatic 

 veins, to which each is connected by means of a small branch which issues from 

 the centre of the lobule (intralobular). The remaining part of the surface of each 

 lobule is imperfectly isolated from the surrounding lobules by a thin stratum of 

 areolar tissue in which is contained a plexus of vessels (the interlobular plexus) 

 and ducts. In some animals, as the pig, the lobules are completely isolated one 

 from another by this interlobular areolar tissue. 



If one of the sublobular veins be laid open, the bases of the lobules may be 

 seen through the thin wall of the vein on which they rest, arranged in the form 

 of a tesselated pavement, the centre of each polygonal space presenting a minute 

 aperture, the mouth of an intralobular vein (Figs. 669 and 671). 



Microscopic Appearance. Each lobule is composed of a mass of cells (hepatic 

 cells) surrounded by a dense capillary plexus, composed of vessels which penetrate 

 from the circumference to the centre of the lobule, and terminate in a single 



