THE INTESTINE 



501 



common mesentery; it is a relatively wide fold. The left part of the duodenum is 

 connected with the mesocolon by a peritoneal fold; this fold has a free posterior 

 border which is clearly seen when the posterior flexure of the duodenum is drawn 

 away from the sublumbar region. The first part of the mesoduodenum contains 

 the right branch of the pancreas. Its root is blended with the mesocolon to form a 

 common mesentery. The remainder of the small intestine forms numerous coils, 

 and is attached by a wide mesentery to the sublumbar region. The terminal part 

 (ileum) passes forward in the sublumbar region along the medial surface of the 

 cfficum and opens into the begiiming of the colon at the ileo-coUc orifice (Ostium 



Fig. 442. — Deep Dissection of Abdominal Viscera of Dog (Female). 



Bl., Bladder; B, body. C, C, cornua of uterus; O, O', ovaries; L. k., left kidney. The concealed part of the colon 



is indicated by dotted lines. The spleen is drawn backward and outward. 



ileocolicum). The bile duct and smaller pancreatic duct open into the duodenum 

 about two or three inches (ca. 5 to 8 cm.) from the pylorus; the larger pancreatic 

 duct opens an inch or two (ca. 2.5 to 5 cm.) further back. The mucous membrane 

 has very long, thin villi. The duodenal glands occur only close to the pylorus. 

 Aggregated lymph nodules or Peyer's patches are numerous (about twenty in 

 young subjects), and begin in the duodenum. They are usually elliptical in out- 

 line, but the last one is band-like, reaches to the end of the ileum, and is four to 

 sixteen inches (ca. 10 to 40 cm.) long in young dogs (Ellenberger) . There is an ileo- 

 colic valve. 1 The muscular coat is relatively thick. 



^ The valve does not seem always to be efficient, since experience shows that rectal injections 

 can be made to pass beyond it. This may be partly due also to the fact that the terminal part of 

 the ileum runs horizontally forward, and its orifice faces forward into the beginning of the colon. 



