STRUCTURE OF THE LIVER. 403 



the principal branches of these veins ramify in the spaces between the 

 lobules, they are termed mter-lobular veins. On the other hand, the 

 branches of the Hepatic Vein pass from the trunk to the centre of each 

 lobule, from which they send out diverging capillary twigs (1, 1,) to- 

 wards the circumference ; and these last, coming into connexion with 

 the converging capillaries of the portal vein, establish a free capillary 

 communication between the interior and exterior of each lobule. Thus 

 the portal blood is first distributed to its exterior, then penetrates its 

 substance, and then, after permeating the parenchymatous substance 

 in numerous minutely-divided streams, is collected and carried off by 

 the hepatic vein, of which a twig originates in the centre of each lobule. 

 Owing to the peculiar position of the branches of the hepatic vein in 

 the centre of each lobule, the lobules are appended to its main trunks 

 almost in the manner of leaves upon a stem (Fig. 120). The precise 

 relation of the capillaries of the hepatic artery with those of the portal 



Fig. 120. 



Connexion of the lobules of the Liver with the Hepatic vein: 1, trunk of the vein; 2, 2, lobules depend- 

 ing from its branches, like leaves on a tree ; the centre of each being occupied by a venous twig, the Intra- 

 lobular Vein. 



and venous systems has not yet been well ascertained ; but there seems 

 reason to believe, with Mr. Kiernan, that the arterial capillaries dis- 

 charge themselves into the ultimate ramifications of the portal vein ; 

 and that thus the blood of the former, having become venous by trans- 

 mission through the nutritive capillaries of the liver, mingles with the 

 other venous blood collected by the venae portse, to supply the mate- 

 rials of the secretory function, which are eliminated from it during its 

 passage into the hepatic vein. 



723. The Hepatic Ducts also seem to form a plexus which surrounds 

 the lobules, connecting them together, and sending branches towards 

 the interior of each. The mode in which they terminate, however, and 

 the precise relation in which they stand to the hepatic cells, which form 

 nearly the entire parenchyma of the Gland, has not yet been com- 

 pletely elucidated. There seems reason to believe, however, that the 

 tubular plexus extends throughout the substance of the lobule, filling 

 up the entire space not occupied by the blood-vessels (its membranous 

 wall, however, being with difficulty traceable, owing to its extreme 

 tenuity) ; and that the hepatic cells are contained within it, as within 

 the follicles or tubes of ordinary glands. These cells (which are easily 

 obtained in a separate condition by scraping a piece of fresh Liver) 

 are of a flattened spheroidal or polygonal form ; and their diameter is 

 usually from l-800th to l-1600th of an inch. Each cell presents a dis- 



