104 THE GALL-BLADDER. 



tarum.* The lymphatic vessels are united to those which 

 are found on the lower surface of the liver, and the nerves are 

 derived from the hepatic plexus. 



The gall-bladder appears to be merely a reservoir, into 

 which bile passes through its duct in a retrograde direction. 

 If air be blown through the hepatic duct from the liver, it will 

 pass to the gall-bladder almost as freely as it passes to the 

 duodenum. 



The biliary duct from the liver, after receiving the duct from 

 the gall-bladder, takes the name of Ductus Communis Chole- 

 dochus. It is wider than either of the other ducts and near 

 three inches in length. It is composed of two tunics, an in- 

 ternal mucus and an external one. The external one, or 

 cellular coat as it has been called, is now generally admitted to 

 be made up of the contractile fibrous tissue, which is a kind 

 of substitute for muscular structure. In some of the lower 

 animals it evidently consists of muscular fibres. It passes 

 down before the vena portarum, and on the right of the hepa- 

 tic artery, to the posterior surface of the right extremity of the 

 pancreas. It passes through a small portion of that gland, and 

 then perforates the muscular coat of the duodenum ; after which 

 it proceeds from half an inch to an inch between this coat and 

 the villous, and opens into the cavity of the intestine. The 

 orifice forms a tubercle which extends lengthwise of the intes- 

 tine, and is rounded above and pointed below, with a slit in it. 

 While this duct is in contact with the pancreas, a duct from that 

 gland generally opens into it, so that the biliary and pancreatic 

 fluids enter the duodenum by the same orifice ; but sometimes 

 the pancreatic duct opens into the duodenum, by a distinct 

 orifice, very near to that of the biliary duct. 



The Bile, or fluid secreted by the liver, appears to answer a twofold purpose in 

 the animal economy. It produces a chemical effect upon the alimentary 

 mixture which passes from the stomach through the intestines; and it 

 increases the peristaltic motion of those important organs. 



By an inverted action of the duodenum, some of this fluid is frequently carried 



* It has been justly observed by John Bell, that the veins would not terminate thus, if 

 bile were secreted by the gall-bladder. 



