DIGESTIVE ORGANS AND THEIR ANATOMY. 291 



the same name, so that we speak of the capsule of Glisson 

 in the liver containing the three ducts just mentioned. 

 These ramifications finally surround the real units of the 

 liver structure, which are the hepatic lobules. These lob- 

 ules are spherical, or on account of being pressed by jux- 

 taposition, polyhedral masses. They are visible to the 

 naked eye, giving to the liver that marked-off appearance 

 readily discernible on a fresh specimen, and accounting for 

 the granular feeling when fried liver is masticated or rolled 

 between the teeth. The lobules are made up of innumerable 

 hepatic cells, arranged mote or less in rows, radiating from 

 the center of each lobule outward. Around and between 

 these lobules the final ramifications, of portal vein, hepatic 

 artery and bile duct run. These end branches are called 

 respectively the interlobular portal vein, the interlobular 

 hepatic artery and the interlobular bile-duct. 



From the plexus of the interlobular portal vein capil- 

 laries arise which run into the lobule from all directions in 

 such a way as to meet in the center. This capillary net- 

 work pervading each lobule is called the lobtilar plexiis. 

 While this lobular plexus is formed mainly from capillaries 

 arising from the portal vein, there seems little doubt but 

 that into this same lobular plexus, blood from the interlob- 

 ular hepatic arteries is poured. We have here then a con- 

 dition of things in which a single capillary plexus is fed by 

 two streams a portal vein and a hepatic artery. The 

 question naturally arises, why this mixing of the blood from 

 the portal vein and hepatic artery might not have occurred 

 before entering the liver at all, doing away with a double 

 system of vessels ramifying throughout the substance of the 

 liver. The explanation is found in the fact that the hepatic 

 artery is used mainly to carry nutritious blood to the various 

 ducts in connection with the liver, and to the connective 

 tissue everywhere pervading it, and that its primary func- 

 tion is not to carry blood to the liver cells themselves. It 

 seems, however, very improbable indeed from the size of 

 the hepatic artery, that all the blood passing through it 



