THE LIVER 165 



blood into the venous plexus at the margin of the lobules, thus 

 providing arterial blood for the lobular parenchyma. 



The hepatic duct is also seen emerging from the transverse fis- 

 sure. (For the sake of clearness, we will trace it from without in- 

 ward.) It follows the course of the portal vein with the hepatic 

 artery. Wherever in a section of the organ the portal is divided, 

 the artery and duct will also appear. Bound together with con- 

 nective tissue, the trio reach the walls of the lobules. The ducts 

 now penetrate the lobule and break up into an exceedingly minute 

 plexus the bile -capillaries. This plexus properly begins in the 

 lobules and drains the bile as formed, passing it into the ducts in a 

 direction opposite to the portal blood -current. 



THE PORTAL CANALS 



If it were possible to grasp the vessels as they are found emerg- 

 ing at the transverse fissure, the portal vein, hepatic artery, and 

 hepatic duct, and to forcibly tear them, with their supporting con- 

 nective tissue, out of the liver, a series of channels or canals would 

 thereby be formed. A portal canal, then, is a space in the liver 

 occupied by branches of the portal vein, the hepatic artery, and the 

 hepatic duct, and the contiguous connective tissue. Frequently more 

 than one specimen of each vessel is to be seen in a canal. There 

 may be two or three veins, and as many arteries and ducts, asso- 

 ciated in a single portal canal. Lymphatic chinks are also abun- 

 dant in this connective tissue. 



From what has been said, it will be understood that a vessel 

 found by itself in this organ must be either an intralobular or a 

 hepatic vein; and these are easily distinguished, as the former are 

 within, while the latter are without the lobules and in the connec- 

 tive tissue framework. On the other hand, a group of vessels will 

 indicate a portal canal, with its large and thin -walled vein, the 

 small thick-walled artery, and, intermediate in size, the duct. 



THE LOBULAR PARENCHYMA 



The lobules consist of two capillary plexuses, one containing 

 blood and the other bile. In the meshes of this network, the 

 hepatic cells are located. 



The blood -capillaries, although extremely tortuous, have a gen- 

 eral direction of convergence toward the central veins. This is 



