THE LIVER. 1065 



continues the course of the hepatic duct, running downward and backward in the 

 hepato-duodenal ligament in front of the portal vein and to the right of the 

 hepatic a'-tery. It passes behind the first portion of the duodenum and then 

 behind and to the inner side of the second portion, lying here in a furrow between 

 duodenum and head of pancreas ; or it may be enclosed by the pancreas till it 

 meets the pancreatic duct. For a short space it is in contact with the right side 

 of this duct. The two perforate the duodenal wall and run obliquely for three- 

 fourths of an inch between the coats. They finally open into a little pouch and 

 that upon a papilla of the mucous membrane by a common orifice, situated near 

 the junction of middle and lower third of the duodenum on its posterior internal 

 wall. This is three or four inches beyond the pylorns. (See Pancreas.) 



When the gall-bladder is distended with bile or calculi, the fundus may be felt through the 

 abdominal parietes, especially in an emaciated subject : the relations of this sac will also serve to 

 explain the occasional occurrence of abdominal biliary fistuia3, through which biliary calculi may 

 pass out. and of the passage of calculi from the gall-bladder into the stomach, duodenum, or 

 colon, which occasionally happens. 



Structure. The gall-bladder consists of three coats serous, fibrous and mus- 

 cular, and mucous. 



The external or serous coat is derived from the peritoneum ; it completely 

 invests the fundus, but covers the body and neck only on their under surface. 



The fibro-muscular coat is a thin but strong layer which forms the framework 

 of the sac, consisting of dense fibrous tissue which interlaces in all directions and 

 is mixed with plain muscular fibres which are disposed chiefly in a longitudinal 

 direction, a few running transversely. 



The internal or mucous coat is loosely connected with the fibrous layer. It is 

 generally tinged with a yellowish-brown color, and is everywhere elevated into 

 minute rugse, by the union of which numerous meshes are formed, 

 the depressed intervening spaces having a polygonal outline. The 

 meshes are smaller at the fundus and neck, being most developed 

 about the centre of the sac. 



The mucous membrane is covered with columnar epithelium 

 and secretes an abundance of thick viscid mucus ; it is continuous 

 through the hepatic duct with the mucous membrane lining the 

 ducts of the liver, and through the ductus communis choledochus 

 with the mucous membrane of the alimentary canal. 



In the cystic duct the mucous membrane is raised into ob- 

 lique crescentic folds much as in the neck of the bladder. It 

 presents the appearance of a continuous spiral valve of which 

 we have seen indications in the small intestine and rectum (Fi**. 

 678). This is the valve of Heister (1758). The outer surface 

 of the duct presents indentations at the attachment of these folds, 

 giving it a sacculated or twisted appearance (Fig. 677). 



The coats of the larger ducts are an external or fibrous and an internal or 

 mucous. The fibrous coat is composed of strong fibro-areolar tissue, with a cer- 

 tain amount of muscular tissue arranged for the most part in a circular manner 

 around the duct. The mucous coat is continuous with the lining membrane of 

 the hepatic duet and gall-bladder, and also with that of the duodenum, and, like 

 the mucous membrane of these structures, its epithelium is of the columnar 

 variety. It is provided with numerous tubules, which are lobulated and open by 

 minute orifices scattered irregularly (Fig. 675). 



Surface Form. 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 c-artilasres, 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 by a line drawn from the articulation of the fifth right costal cartilage to the sternum 

 horizontally outward to a little below the nipple, and then inclined downward to reach the 

 seventh rib at the side of the chest. The upper limit of the left lobe may be defined by continu- 

 ing this line to the left, with an inclination downward as it crosses the gladiolus, to a point about 



