DIGESTIVE GLANDS. 221 



the foramen of Winslow to open into the descending 

 part of the duodenum three and one-half to four 

 inches beyond the pylorus. It passes obliquely 

 through the intestinal wall, where it is joined by the 

 pancreatic duct, and opens by a common orifice on 

 the bile papilla, as already described. The common 

 bile duct is about three inches long and one-quarter 

 inch in diameter. 



The histology of the bile ducts resembles that of the 

 gall bladder. There is on the inside a mucous mem- 

 brane clothed with simple columnar epithelium rest- 

 ing upon a base- 

 ment membrane. Lymphatics. 



\\ 



Smooth muscle 



cells are found in tl/ vw ^ 



X \W&%*&& Bile duct. 



the membrana 



propriaof themu- 

 cosa. The sub- ^ 

 mucosa is a nar- 

 row Vascular layer Fig. 167. Section of portal canal of liver. 



composed of con- 

 nective-tissue elements. The muscularis consists of 

 an inner circular layer and an outer longitudinal 

 layer of smooth muscle. On the outside is a strong 

 connective-tissue coat whose fibers are continuous 

 with the capsule of Glisson. 



The passage of bile into the intestine is not a pas- 

 sive but an active process. The smooth muscle of 

 the bile duct contracts in a peristaltic manner, and 

 the bile is thus expelled into the intestine, periodi- 

 cally, in jets. This activity is normally under con- 

 trol of the nerves, largely a reflex action of the sym- 



