LIVER. 85 



spaces between the cells by open orifices, has not been satisfactorily deter- 

 mined. 



The Bile Channels empty into the interlobular ducts, which measure 

 about suVff f an mcn m diameter, and are composed of a thin homogeneous 

 membrane lined by flattened epithelial cells. 



As the interlobular bile ducts unite to form larger trunks, they receive 

 an external coat of fibrous tissue, which strengthens their walls; they 

 finally unite to form one large duct, the hepatic duct, which joins the cystic 

 duct ; the union of the two forms the ductus communis choledochus, which 

 is about three inches in length, the size of a goose quill, and opens into the 

 duodenum. 



The Gall Bladder is a pear-shaped sack, about four inches in length, 

 situated in a fossa on the under surface of the liver. It is a reservoir for 

 the bile, and is capable of holding about one ounce and a half of fluid. It 

 is composed of three coats, (l) serous, a reflection of the peritoneum, (2) 

 fibrous and muscular, (3) mucous. 



Functions of the Liver. The liver is a complex organ having a 

 variety of relations to the general processes of the body. While its physio- 

 logical actions are not yet wholly understood, it may be said that it 



1. Secretes bile. 



2. Forms glycogen. 



3. Assists in the formation of urea and allied products. 



4. Modifies the composition of the blood as it passes through it. . 



The Secretion of Bile. The characteristic constituents of the bile do 

 not preexist in the blood, but are formed within the interior of the liver 

 cells out of materials derived from the venous and arterial blood. The 

 hepatic cells absorbing these'materials elaborate them into bile elements; and 

 in so doing undergo histological changes similar to those exhibited by other 

 secretory glands. The bile once formed, it passes into the mouths of 

 the bile capillaries, near the periphery of the lobules. Under the influence 

 of the vis-a-tergo of the new formed bile it flows from the smaller into the 

 larger bile ducts, and finally empties into the intestine, or is regurgitated 

 into the gall bladder, where it is stored up until it is required for the 

 digestive process in the small intestine. The study of the secretion of bile 

 by means of biliary fistulae reveals the facts that the secretion is continuous 

 and not intermittent ; that the hepatic cells are constantly pouring bile into 

 the ducts which convey it into the gall bladder. As this fluid is required 

 only during intestinal digestion, it is only then that the walls of the gall 

 bladder contract and discharge it into the intestine. 



