Chap. XIV] THE DIGESTIVE SYSTEM 277 



are called intralobular (within the lobule). These vessels con- 

 verge toward the centre of the lobule like the spokes of a wheel 

 and empty into a vein (intralobular) which carries the blood 

 away from the lobule. The intralobular veins from a number 

 of lobules empty into a much larger vein upon whose surface a 

 vast number of lobules rest, and therefore the name sublobular 

 (under the lobule) is given to this kind of veins. They empty 

 into still larger veins, the hepatic, which converge to a few large 

 trunks and terminate in the inferior vena cava, which is em- 

 bedded in the posterior surface of the gland. 



The bile ducts. — The surfaces of the hepatic cells are grooved, 

 and the grooves on two adjacent cells fit together and form a 

 channel into which the bile is poured as soon as it is formed by 

 the cells. These channels form a network between and around 

 the cells as intricate as the network of blood-vessels. They are 

 called intralobular ducts, and empty into larger ducts called in- 

 terlobular. These unite and form larger and larger ducts until 

 two main ducts, one from the right and one from the left side 

 of the liver, unite in the portal fissure and form the hepatic duct. 



The hepatic duct runs downward and to the right for about 

 two inches (50 mm.) and then joins at an acute angle the duct 

 from the gall-bladder, termed the cystic duct. The hepatic and 

 cystic ducts together form the common bile duct {ductus com- 

 munis choledochus) , which runs downward for about three inches 

 (75 mm.) and enters the duodenum about three inches (75 mm.) 

 below the pylorus. This orifice serves as a common opening for 

 both the common bile and the pancreatic duct. It is very small 

 and is guarded by a sphincter muscle which keeps it closed except 

 during digestion. (See Fig. 158.) 



Hepatic artery. — We must remember that the blood brought 

 to the liver by the portal vein is venous blood from the stomach, 

 spleen, pancreas, and intestines. It is rich with the products of 

 digestion and intended for the manufacture of bile, etc. It 

 is not intended for purposes of nourishment of the liver itself, 

 hence arterial blood is furnished by the hepatic artery. It enters 

 the liver with the portal vein, divides and subdivides in the same 

 way, thus forming another network between the lobules, and in 

 the lobules between the cells. The capillaries from the portal 

 vein and the hepatic artery are separate and distinct until, near 



