THE LIVER. 



939 



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 (Fig. 514). 



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 



He P atic 

 artery. 



Portal vein 



Orifices of intralobular veins. 



FIG. 514. Longitudinal section of an hepatic 

 vein. (After Kiernan.) 



of 



canal from 

 which vein 

 has been 

 removed. 



FIG. 515. Longitudinal section of a small portal 

 vein and canal. (After Kiernaii.j 



straight vein, which runs through its centre, to open at its base into one of 

 the radicles of the hepatic vein. Between the cells are also the minute com- 

 mencements of the bile-ducts. Therefore in the lobule we have all the essen- 

 tials of a secreting gland ; that is to say : (1) cells, by which the secretion is 

 formed ; (2) blood-vessels, in close relation with the cells, containing the blood 

 from which the secretion is derived ; and (3) ducts, by which the secretion, 

 when formed, is carried away. Each of these structures will have to be further 

 considered. 



(1) The hepatic cells are of more or less spheroidal form, but may be rounded, 

 flattened, or many-sided from mutual compression. They vary in size from the 

 j-flVfi- to the 2iroT f an i ncn i Q diameter. They consist of a honeycomb net- 

 work (Klein) without any cell-wall, and contain one or sometimes two distinct 

 nuclei. In the nucleus is a highly refracting nucleolus with granules. Embedded 

 in the honeycomb network are numerous yellow particles, the coloring matter of 

 the bile, and oil-globules. The cells adhere together by their surfaces so as to 

 form rows, which radiate from the centre to the circumference of the lobules. 1 As 

 stated above, they are the chief agents in the secretion of the bile. 



(2) The Blood-vessels. The blood in the capillary plexus around the liver- 

 cells is brought to the liver principally by the portal vein, but also to a certain 

 extent by the hepatic artery. For the sake of clearness the distribution of the 

 blood derived from the hepatic artery may be considered first. 



1 Dele"pine states that there are evidences of the arrangement of these cells in the form of col- 

 umns, which form tubes with narrow lumina branching from terminal bile-ducts. This branching is 

 evidenced by a divergence of the columns from lines extending between adjacent portal vessels. The 

 columns of cells group round terminal bile-ducts, and not round the so-called intralobular veins. 

 (Lancet, 1895, vol. i., p. 1254.) 



