THE INTESTINES 235 



able in calibre, namely, the small intestine (intestinum tenue) and 

 the large intestine (intestinum crassum). Both are greatly elon- 

 gated and convoluted. In examining them, care must be taken to 

 avoid injury to the blood-vessels and mesenteries, especially the 

 dorsal 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. 100, 136. 

 For study of mucous surface, see note p. 367. 



1. Beginning at the pylorus, trace the course of the small intestine* 

 as follows: Its first portion, the duodenum, curves round from 

 the pylorus to turn back and form a U-shaped loop lying on 

 the dorsal wall of the adbominal cavity to the right of the 

 vertebral column. The distal end of this portion of the intestine, 

 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. At its connection with the caecum, 

 the small intestine forms a rounded, semi-expanded sac, the 

 sacculus rotundus, a feature peculiar to the rabbit. The termi- 

 nal 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 portion is the short part which curves round 

 from the pylorus to lead into a long descending portion. 

 The latter is then connected by a short, wavy, transverse 

 (horizontal) portion with an ascending portion of inter- 

 mediate length. 



(6) 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. 



