300 THE ORGANS 



sists of only two rows of cells (Figs. 201 and 202), between which lies 

 the lumen. The latter is thus never in touch with more than two cells. 



The end-to-end anastomosis of the secreting tubules, there being 

 no true terminal tubules; anastomosis of neighboring tubules by 

 means of side branches; the arrangement of the bile capillaries in such 

 a manner that a single Kver cell abuts upon more than one capillary. 



The more intimate relation of the liver cell to the blood capillaries. 

 Thus most gland cells have one side on the lumen, one side only in 

 contact with a capillary blood-vessel, the remaining sides being in 

 contact with other cells of the same tubule. A Hver cell, on the 

 other hand, may and usually does come in contact with several blood 

 capillaries (Fig. 202). 



TJie arrangement of both blood-vessels and tubules within the lobule. 

 In the submaxillary, for example, the terminal tubules are con- 

 voluted and run in all directions. In the liver the terminal tubules 

 are straight and run in a definite direction from the periphery of the 

 lobule toward the centre. Again, while in other glands both intra- 

 lobular arteries and ducts are distributed outward from the centre of 

 the lobule, and the blood is returned through veins which pass to 

 the periphery of the lobule, in the liver the interlobular ducts pass to 

 the periphery of the lobule and give off secreting tubules which pass 

 in toward the centre of the lobule. The afferent vessels also (portal 

 veins) take the blood to the periphery of the lobule and distribute 

 it to a capillary network which converges to an efferent vessel 

 (hepatic vein) at the centre of the lobule. The veins are also pecu- 

 liar in that they do not follow the arteries in leaving the Hver but 

 pursue an entirely independent course (compare Figs. 204 and 205). 



Blood-vessels. — These have been alreadv described. 



Lymph vessels form a network in the Hver capsule. These com- 

 municate with deep lymphatics in the substance of the organ. The 

 latter accompany the portal vein and follow the ramifications of its 

 capillaries within the lobule as far as the central vein. 



The nerves of the liver are mainly non-medullated axones of 

 sympathetic neurones. The nerves accompany the blood-vessels 

 and bile ducts, around which they form plexuses. These plexuses 

 give off fibrils which end on the blood-vessels, bile ducts, and liver 

 cells. 



Three main ducts, all parts of a single excretory duct system, are 

 concerned in the transportation of the bile to the intestine, the hepatic, 

 the cystic, and the common. Their walls consist of a mucous membrane. 



