THE LIVER. 



941 



Several views have prevailed as to the mode of origin of the hepatic ducts ; it 

 seems, however, to be clear that they commence by little passages which are formed 

 between the cells, and which have been termed intercellular biliary passages or 

 bile-capillaries. These passages are merely little channels or spaces left between 



the contiguous surfaces of two cells or in 

 the angle where three or more liver-cells 

 meet (Fig. 517), and it seems doubtful 

 whether there is any delicate membrane 



^Biliary 

 duct. 



Hepatic 



cells. 



'\ 



Capillary. 



Biliary duct 



FIG. 517. Section of liver. 



TIG. 518. A transverse section of a small portal 

 canal and its vessels. < After Kiernan.) 1. Portal vein. 

 2. Interlobular branches. 8. Vaginal branches. 4. 

 Hepatic duct. 5. Hepatic artery. 



forming the wall of the channel. The channels thus formed radiate to the circum- 

 ference of the lobule, and, piercing its wall, form a plexus (interlobular) between 

 the lobules. From this plexus ducts are derived which pass into the portal canals, 

 become enclosed in Glisson's capsule, and, accompanying the portal vein and 

 hepatic artery (Fig. 518), join with other ducts to form two main trunks, which 

 leave the liver at the transverse fissure, and by their union form the hepatic duct. 



Structure. The coats of the smallest biliary ducts, which lie in the interlobular 

 spaces, are a connective- tissue coat, in which are muscle-cells, arranged both cir- 

 cularly and longitudinally, and an epithelial layer, consisting of short columnar 

 cells. In the larger ducts, which lie in the portal canals, there are a number of 

 orifices disposed in two longitudinal rows, which were formerly regarded as the 

 openings of mucous glands, but which are merely the orifices of tubular recesses. 

 They occasionally anastomose, and from the sides of them saccular dilatations are 

 given off. 



Lymphatics of the Liver. The lymphatics in the substance of the liver com- 

 mence in lymphatic spaces around the capillaries of the lobules ; they accompany 

 the vessels of the interlobular plexus, often enclosing and surrounding them. These 

 unite arid form larger vessels, which run in the portal canals, enclosed in Glisson's 

 capsule, and emerge at the portal fissure to be distributed in the manner described. 

 Other superficial lymphatics form a close plexus, under the peritoneum, where this 

 membrane covers the liver, and pass in various directions through the ligaments of 

 the liver (page 634). 



Nerves of the Liver. The nerves of the liver derived from the pneumogastric 

 and sympathetic enter the liver at the transverse fissure and accompany the vessels 

 and ducts to the interlobular spaces. Here, according to Korolkow, the medul- 

 lated fibres are distributed almost exclusively to the coats of the blood-vessels ; 

 while the non-medullated enter the lobules and ramify between the cells. 



The Excretory Apparatus of the Liver. 



The excretory apparatus of the liver consists of (1) the hepatic duct, which, 

 as we have seen, is formed by the junction of the two main ducts, which pass out 

 of the liver at the transverse fissure, and are formed by the union of the bile-capil- 



