210 THE MICROSCOPIST. 



and their structure is similar to the follicles of a lymphatic 

 gland. The gland vesicles of the pancreas are roundish, 

 and like other salivary glands it is invested with a vascu- 

 lar network with rounded meshes. 



The liver is the largest gland connected with nutrition. 

 Few animals are without a liver or its structural equiva- 

 lent. In polyps the liver is represented by colored cells 

 in the walls of the stomach cavity. In annelids the biliary 

 cells cluster round csecal prolongations of the digestive 

 cavity. In Crustacea the liver consists of follicles, and in 

 insects of tubes, opening into the intestine. In all cases 

 the essential elements are glandular cells containing col- 

 oring matter, oil, etc. In vertebrates some parts of the 

 structure have not been decided upon without controversy. 



In man the liver is a large, solid, reddish-brown gland, 

 about twelve inches across, and six or seven inches from 

 anterior to posterior edge, and weighing three or four 

 pounds, situated in the right hypochondrium, and reach- 

 ing over to the left. It is divisible into right and left 

 lobes by the broad peritoneal ligament above, and the 

 longitudinal fissure beneath. From the latter a groove 

 passes transversely on the right side, lodging the biliary 

 ducts, sinus of the portal vein, hepatic artery, lymphatics, 

 and nerves, which are enveloped in areolar tissue, called 

 the capsule of Glisson. From this groove ramifications 

 of the portal canal extend through the liver, so numerous 

 that no part of the hepatic substance is further than one- 

 thirtieth of an inch from them. These ramifications 

 carry the branches of the portal vein from which the 

 capillary plexus surrounding the lobules begin, together 

 with the bile-ducts, hepatic artery, etc. 



The hepatic lobules are readily distinguished by the 

 naked eye in many mammals, as the hog, but less easily 

 in human liver. They consist essentially of innumerable 

 gland-cells, and a complex network of vessels which tend 

 towards the centre of the lobule, where their confluence 



