THE LIVER. 943 



The Cystic Duct, the smallest of the three biliary ducts, is about an inch and a 

 half in length. It passes obliquely downward and to the left from the neck of 

 the gall-bladder, and joins the hepatic duct to form the common bile-duct. It lies 

 in the gastro-hepatic omentum in front of the vena portae, the hepatic artery lying 

 to its left side. The mucous membrane lining its interior is thrown into a series 

 of crescentic folds, from five to twelve in number, similar to those found in the 

 neck of the gall-bladder. They project into the duct in regular succession, and 

 are directed obliquely round the tube, presenting much the appearance of a con- 

 tinuous spiral valve. When the duct is distended, the spaces between the folds are 

 dilated, so as to give to its exterior a sacculated appearance. 



The Ductus Communis Choledochus, or common bile-duct, the largest of the three, 

 is the common excretory duct of the liver and gall-bladder. It is about three 

 inches in length, of the diameter of a goose-quill, and formed by the junction of 

 the cystic and hepatic ducts. 



It descends along the right border of the lesser omentum behind the first por- 

 tion of the duodenum, in front of the vena portse, and to the right of the hepatic 

 artery ; it then passes between the pancreas and descending portion of the duo- 

 denum, and running for a short distance along the right side of the pancreatic 

 duct, near its termination, passes with it obliquely between the mucous and mus- 

 cular coats. The two ducts open by a common orifice upon the summit of a papilla, 

 situated at the inner side of the descending portion of the duodenum, a little below 

 its middle and about three or four inches below the pylorus. 



Structure. The coats of the large biliary ducts are an external or fibrous, and 

 an internal or mucous. The fibrous coat is composed of strong fibro-areolar tissue, 

 with a cei'tain amount of muscular tissue arranged, for the most part, in a circu- 

 lar manner around the duct. The mucous coat is continuous with the lining mem- 

 brane of the hepatic ducts and gall-bladder, and also with that of the duodenum ; 

 and, like the mucous membrane of these structures, its epithelium is of the col- 

 umnar variety. It is provided with numerous mucous glands, which are tabulated 

 and open by minute orifices scattered irregularly in the larger ducts. The coats 

 of the smallest biliary ducts, which lie in the interlobular spaces, are a connective- 

 tissue coat, in which, according to Heidenhain, are muscle-cells arranged both cir- 

 cularly and longitudinally, and an epithelial layer, consisting of short columnar 

 cells. 



Surface Relations. The liver is situated in the right hypochondriac and the epigastric 

 regions, and is moulded to the arch of the Diaphragm. In the greater part of its extent it 

 lies under cover of the lower ribs and their cartilages, but in the epigastric region it comes 

 in contact with the abdominal wall, in the subcostal angle. The upper limit of the right 

 lobe of the liver may be defined in the middle line by the junction of the mesostermim with the 

 ensiform cartilage; on the right side the line must be carried upward as far as the fifth rib car- 

 tilage in the line of the nipple and then downward to reach the seventh rib at the side of the chest. 

 The upper limit of the left lobe maybe defined by continuing this line to the left with an inclina- 

 tion downward to a point about two inches to the left of the sternum on a level with the sixth 

 left costal cartilage. The lower limit of the liver may be indicated by a line drawn half an inch 

 below the lower border of the thorax on the right side as far as the ninth right costal cartilage, 

 and thence obliquely upward across the subcostal angle to the eighth left costal cartilage. A 

 slight curved line with its convexity to the left from this point i. e., the eighth left costal 

 cartilage to the termination of the line indicating the upper limit will denote the left margin 

 of the liver. The fundus of the gall-bladder approaches the surface behind the anterior 

 extremity of the ninth costal cartilage, close to the outer margin of the Right rectus muscle. 



It must be remembered that the liver is subject to considerable alterations in position, and 

 the student should make himself acquainted with the different circumstances under which this 

 occurs, as they are of importance in determining the existence of enlargement or other diseases 

 of the organ. 



Its position varies according to the posture of the body. In the erect position in the adult 

 male the edge of the liver projects about half an inch below the lower edge of the right costal 

 cartilages, and its anterior border can be often felt in this situation if the abdominal wall is thin. 

 In the supine position the liver gravitates backward and recedes above the lower margin of the 

 ribs, and cannot then be detected by the finger. In the prone position it falls forward, and can 

 then generally be felt in a patient with loose and lax abdominal walls. Its position varies also 

 with the ascent or descent of the Diaphragm. In a deep inspiration the liver descends below 

 the ribs; in expiration it is raised behind them. Again, in emphysema, where the lungs are 



