THE INTESTINES. 189 
attachments of the mesenteries, in which the chief plexuses and 
related ganglia of the sympathetic system will afterwards be traced. 
(For the general relations of the intestines and mesenteries, see pp. 82, 99.) 
I. Beginning at the pylorus, trace the course of the small 
intestine, as follows: Its first portion, the duodenum, forms a 
U-shaped loop lying on the dorsal wall of the abdominal cavity 
to the right of the vertebral column. The distal end of this loop, 
when traced from the right side, disappears in the peritoneum and 
may then be picked up in a forward position on the left side.of the 
mass. This point marks the beginning of the second portion, the 
mesenterial small intestine (intestinum tenue mesenteriale), 
which may be traced to its termination on the greatly enlarged 
caecum. The connection with the caecum is through a rounded 
semi-expanded sac, the sacculus rotundus. The _ terminal 
portion of the small intestine is somewhat more difficult to follow 
on account of the adhesions of its peritoneum with that of the large 
intestine. 
2. Examine the divisions of the duodenal loop and related 
structures, as follows: 
(a) The superior, descending, transverse (horizontal), and 
ascending portions of the duodenal loop. 
(b) The common bile duct, opening on the dorsal wall of the 
superior portion. 
(c) The mesoduodenum, a fold of peritoneum joining the 
various parts of the loop. 
(d) The pancreas (Fig. 3 B, p. 22). Its principal portion is 
here seen as a diffuse brownish mass lying in the mesoduo- 
denum. Its duct (d. pancreatis) opens into the posterior 
portion of the ascending limb. 
(e) The superior pancreaticoduodenal artery, a branch of 
the gastroduodenal (see p. 185), passes backward on the first 
portion of the descending limb. 
(f{) The inferior pancreaticoduodenal artery (a. pancreatico- 
duodenalis inferior), a branch of the superior mesenteric 
(p. 192), enters the mesoduodenum from the left side and 
supplies the major portion of the loop. An anterior branch 
anastomoses with (e). 
