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 
cecum and opens into the beginning of the colon at the ileo-colic orifice (Ostium 
Fic. 442—Drep Dissection oF ABDOMINAL VISCERA OF Doa (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 em.) from the pylorus; the larger pancreatic 
duct opens an inch or two (ca. 2.5 to 5 em.) 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 em.) long in young dogs (Ellenberger). 
There is an ileo- 
‘colic valve! The muscular coat is relatively thick. 
1 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 
jthe ileum runs horizontally forward, and its orifice faces forward into the beginning of the colon. 
