124 ELEMENTS OF MAMMALIAN ANATOMY. 
close along the concavity of the duodenum. It has two 
ducts, one of which enters the duodenum in common with 
the common bile duct, while the other enters about three 
centimeters further caudad. The pancreatic juice acts on 
the starches, proteids, and fats. 
THE PERITONEUM. 
The peritoneum (Fig. 61) is the serous sac lining the 
abdominal cavity and investing most of the organs therein 
contained. The four portions of the peritoneum are known 
as the omenta, the mesenterics, parietes, and ligaments. 
The omenta are three in number, the largest of which is 
the great or gastrocolic omentum, stretching caudad from 
the dorsal abdominal wall and the greater curvature of the 
stomach, so as to cover the intestine like an apron. It is 
composed of four layers of peritoneum forming a closed 
sac, and bearing more or less fat. Two layers form the 
ventral wall of the sac attached to the stomach, and two 
layers are also present in the dorsal wall of the sac which 
invests the pancreas. 
The lesser omentum, or gastrohepatic omentum, extends 
caudad from the liver to the pyloric part of the stomach 
and duodenum. Its two folds extend from the two sides 
of the portal fissure, ensheathing the portal vein, hepatic 
artery, and cystic duct. The gastrosplenic omentum stretches 
from the cardiac region of the stomach to the spleen, which 
it embraces, and then proceeds to the diaphragm. 
The mesenteries are the two layers of peritoneum 
suspending the intestine from the dorsal abdominal wall. 
There are four mesenteries: the true mesentery, suspending 
the jejunum and ileum; the mesoduodenum, suspending the 
duodenum; the mesocolon, suspending the colon; and the 
mesorectum, suspending the rectum. 
The parietes or parietal peritoneum is that portion lining 
