THE PANCREAS. 585 



is composed of three coats, serous, fibrous, and mucous. The serous 

 coat is partial, is derived from the peritoneum, and covers that side 

 only which is unattached to the liver. The middle or fibrous coat is a 

 thin but strong fibrous layer, connected on one side to the liver, and on 

 the other to the peritoneum. The internal or mucous coat is but 

 loosely connected Avith the fibrcras layer ; it is everywhere raised into 

 minute rugae, which give it a beautifully reticulated appearance, and 

 forms at the neck of the sac a spiral valve. It is continuous through 

 the hepatic duct with the,niucous membrane lining all the ducts of the 

 liver, and through the ductus communis choledochus, with the mucous 

 membrane of the alimentary canal. 



The Biliary ducts are, the ductus communis choledochus, the cystic, 

 and the hepatic duct. 



The Ductus communis ckoledochus (x<>*.v bilis, &%O/U.KI recipio) is the 

 common excretory duct of the liver and gall-bladder ; it is about three 

 inches in length, and commences upon the papilla, situated on the 

 inner side of the cylinder of the perpendicular portion of the duodenum. 

 Passing obliquely between the mucous and muscular coat, it ascends 

 behind the duodenum, and through the right border of the lesser omen- 

 turn ; and divides into two branches the cystic duct and the hepatic 

 duct. It is constricted at its commencement in the duodenum, and 

 becomes dilated in its progress upwards. 



The Cystic duct, about an inch in length, passes outwards to the neck 

 of the gall-bladder, with which it is continuous. 



The Hepatic duct continues onwards to the transverse fissure of the 

 liver, and divides into two branches, which ramify through the portal 

 canals to every part of the liver. 



The coats of the hepatic ducts are an external or fibrous, and an in- 

 ternal or mucous. The external coat is composed of a contractile 

 fibrous tissue, which is probably muscular ; but its muscularity has 

 not yet been demonstrated in the human subject. The mucous coat 

 is continuous on the one hand with the lining membrane of the 

 hepatic ducts and gall-bladder, and on the other with that of the 

 duodenum. 



Vessels and Nerves. The gall-bladder is supplied with blood by 

 the cystic artery, a branch of the hepatic. Its veins return their 

 blood into the portal vein. The nerves are derived from the hepatic 

 plexus. 



THE PANCREAS. 



The Pancreas is a long, flattened, conglomerate gland, analogous to 

 the salivary glands. It is about six inches in length, and between 

 three and four ounces in weight ; is situated transversely across the 

 posterior wall of the abdomen, behind the stomach, and resting upon 

 the aorta, vena portae, inferior vena cava, the origin of the superior 

 mesenteric artery, and the left kidney and supra-renal capsule ; oppo- 

 site the first and second lumbar vertebrae. It is divided into a body, 

 a greater, and a smaller extremity ; the great end or head is placed 



