THE ALIMENTARY CANAL AND ITS APPENDAGES. 345 



larger blood-vessels, and branches of the hepatic duct. The 

 hepatic cells are the proper tissue elements of the liver, all 

 the rest being subsidiary arrangements for their nutrition 

 and protection. Each is polygonal, nucleated and very 

 granular, and has a diameter of about .025 millimeter ( T oVo^ 

 of an inch). In each lobule they are arranged in rows or 

 strings, which form a network, in the meshes of which the 

 blood-capillaries run. Covering the surface of the liver 

 is a layer of the peritoneum, beneath which is a dense 



FIG. 117. A lobule of the liver, magnified, showing the hepatic cells radiately 

 arranged around the central imralobulur vein, and the lobular capillaries inter- 

 laced with them. 



connective-tissue layer, forming the capsule of Glisson. At 

 the portal fissure offsets from this capsule run in, and line 

 canals, the portal canals, which are tunnelled through the 

 organ. These, becoming smaller and smaller as they branch, 

 finally become indistinguishable close to the ultimate 

 lobules. From their walls and from the external capsule, 

 connective-tissue partitions radiate in all directions through 

 the liver and, support its other parts. In each portal canal 

 lie three vessels a branch of the portal vein, a branch of 

 the hepatic artery, and a branch of the hepatic duct; the 

 division of the portal vein being much the largest of the 

 three. These vessels break up as the portal canals do, and 

 all end in minute branches around the lobules. The blood 

 carried in by the portal vein (which has already circulated 

 through the capillaries of the stomach, spleen, intestines and 



