484 TEXT-BOOK OF PHYSIOLOGY 



and hence are in close relation to capillary blood-vessels, lymph spaces, 

 nerves, and irregular channels or passageways. The latter running between 

 the epithelial cells may be compared to the lumen of other secreting glands. 

 Blood-vessels and Their Distribution. The blood-vessels which are 

 in relation with the liver are: 



1. The portal vein. 



2. The hepatic artery. 



3. The hepatic vein. 



The portal vein and the hepatic artery enter the liver at the transverse 

 fissure. After penetrating its substance they divide and subdivide into 

 smaller and smaller branches', which ulimately occupy the space between the 

 lobules, completely surrounding and lim- 

 iting them. From their situation they are 

 termed interlobular veins and arteries. 



The interlobular veins give off small cap- 

 illary vessels which penetrate the lobule at LB^&foBt&SS&ai , central vein. 

 all points of its surface. These capillaries, 





Interlobular vein. Hepatic duct. 



FIG. 219. SCHEME or A HEPATIC 

 LOBULE, REPRESENTED IN TRANSVERSE 

 SECTION BELOW AND, BY PARTIAL LEV- 

 FIG. 218. SECTION OF LIVER OF PIG, SHOWING ELING, IN LONGITUDINAL SECTION 

 V^ERY DIAGRAMMATICALLY THE LOBULES, a. Interlobu- ABOVE. In the left half the blood- 

 lar connective tissue, b, c. Branches of portal vein vessels are drawn; in the right half 

 and of hepatic artery, d. Bile-ducts, e. Intralobular only the cords of hepatic cells. X 20. 

 vein. (Pier sol.) (Stohr.) 



though frequently anastomosing, form a radial meshwork which converges 

 toward the center of the lobule. In the meshes of this plexus are found, 

 arranged in a corresponding radial manner, the liver cells. The interlobular 

 arteries are distributed to the walls of the portal vein, to the connective 

 tissue, and finally terminate in the portal vein capillaries. The intralobu- 

 lar capillaries thus receive and transmit blood which is an admixture of both 

 arterial and venous blood. In the center of each lobule there is a large vein, 

 formed by the union of the intralobular capillaries, known as the intralobular 

 vein, which collects all the blood of the lobule and transmits it through the 

 lobule to an underlying or sublobular vein (Fig. 220). These latter vessels, 

 uniting and reuniting, ultimately form the hepatic vein, which empties the 

 blood into the inferior vena cava. 



Bile Capillaries and Hepatic Ducts. The bile capillaries are narrow 

 channels which penetrate the lobule in all directions and are generally found 

 running along the sides of the cells. These channels, which are devoid of 



