358 ABDOMEN 



on the left ; the subserous, muscular, and submucous layers 

 have no special features of importance. There are, how- 

 ever, special features to be noted in association with the 

 mucous layer. It is covered throughout by villi, but plicae 

 circulares are present only in the descending and inferior 

 parts. There, however, they are very large and abundant. 

 In the lower portion of the descending part a longitudinal 

 fold, the plica longitudinalis duodeni, which has already been 

 examined (p. 350), cuts across the line of the plicae circulares. 

 It terminates above at the papilla duodeni, through which 

 the bile and pancreatic juice are poured into the duodenum 



Incisura angularis 



Sphincteric cylinder 



Duodeno-pyloric constriction 



Sphincteric ring 

 Orifice of pyloric canal 



Interior of duodenum 



Sphincteric ring 

 Duodeno-pyloric constriction 



Sphincteric cylinder Pyloric antrum 



FIG. 168. Pyloric Canal and Pyloric Antrum of the Stomach opened up 

 by section in the plane of the two curvatures. 



Opening on the surface of the mucous membrane are the 

 orifices of numerous intestinal glands, and intermingled with 

 them, especially in the pars superior, are the orifices of the 

 special duodenal glands. 



Dissection. Take a segment of the wall of the first part of 

 the duodenum and pin it down, with its mucous surface under- 

 most, to the bottom of a cork-lined tray filled with water. Its 

 coats may then be dissected. They are in all respects similar 

 to those already examined in connection with the jejunum 

 (P- 3 2 5/ H the dissection is carried on until the deep surface 

 of the submucous coat is exposed by the removal of the entire 

 muscular coat, a view of the duodenal glands may be obtained. 

 They appear as whitish specks, about the size of hemp-seed, in 



