THE LIVER 



1195 



medullated fibers are distributed almost exclusively to the coats of the bloodvessels; while the 

 non-medullated enter the lobules and ramify between the cells and even within them. 1 



Intralobular vein 



Intralobular vein 



FIG. 1091. Section of injected liver (dog). 



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

 an extremely fine areolar tissue, in which ramify the portal vein, hepatic ducts, hepatic artery, 

 hepatic veins, lymphatics, and nerves; the whole being invested by a serous and a fibrous coat. 



The serous coat (tunica serosa) 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 (capsida fibrosa 

 [GKssoni]', areolar coat) lies beneath 

 the serous investment, and covers 

 the entire surface of the organ. It 

 is difficult of demonstration, except- 

 ing where the serous coat is defi- 

 cient. At the porta it is continuous 

 with the fibrous capsule of Glisson, 

 and on the surface of the organ with 

 the areolar tissue separating the 



Column of liver- 

 cells 

 Interlobular vein 



Sinusoid- 



lobules. 



The lobules (lobuli hepalis) form 

 the chief niass of the hepatic sub- 

 stance; they may be seen either on 

 the surface of the organ, or by mak- 

 ing a section through the gland, as 

 small granular bodies, about the size 

 of a millet-seed, measuring from 1 to 

 2.5 mm. in diameter. In the human 

 subject their outlines are very irreg- 

 ular; but in some of the lower ani- 

 mals (for example, the pig) they are 

 well-defined, and, when divided 

 transversely, have polygonal out- 

 lines. The bases of the lobules are clustered around the smallest radicles (sublobular) of the 

 hepatic veins, to which each is connected (Fig. 10S9) by means of a small branch which issues 

 from the center 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 from one another by the interlobular areolar tissue 

 (Fig. 1092). 



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 a form resembling a tesselated pavement, 



> Berkeley, Anat., Aug., 8, 1893; MacCallum, A. B., Quart. Jour. Micr. Sci., 1887, 27; Allegra, Anat., Aug. 25, 1904. 



Intralobular vein 



Sublobular vein 



FIG. 1092. A single lobule of the liver of a pig. X 60. 





