THE COELOM, DIGESTIVE, AND RESPIRATORY SYSTEMS 193 



located. The common slightly swollen chamber where bile and pancreatic ducts 

 unite is known as the ampulla of Vater. The second or accessory pancreatic duct 

 in the cat enters the duodenum about three-quarters of an inch caudad of the 

 principal duct but is not easy to find. 



From the duodenum trace the coils of the remainder of the small intestine. 

 It is supported by a part of the dorsal mesentery, the mesentery proper. The 

 first portion of the small intestine beyond the duodenum is called the jejunum, 

 and the remainder, the ileum, but there is no definite boundary between the two. 

 Note the coils of the mesentery accompanying the intestine and the frequent 

 fusions which occur (especially in the rabbit) between these coils. In the cat 

 it will be necessary to withdraw the greater omentum from the coils of the 

 intestine; the omentum may then be cut across near the spleen and discarded. 

 Follow the small intestine to its enlargement into the large intestine. In doing 

 this it may be necessary to tear slightly the fusions of the mesentery, but the 

 structures should be kept as intact as practicable. 



Rabbit: At the point of juncture of the large and small intestine there is an 

 enlargement, the sacculus rotundus. From the sacculus rotundus extends an 

 enormous blind sac, about a foot and a half in length. The first foot of this is 

 very large and is known as the caecum; the last five or six inches is reduced in 

 diameter and constitutes the vermiform appendix. Both caecum and appendix 

 are very much longer in the rabbit than in most mammals, owing probably 

 to the habit of the animal of ingesting large quantities of vegetable food. The 

 wall of the caecum is marked by a spiral line which denotes the position of an 

 internal spiral fold of the lining membrane of the caecum. From the sacculus 

 rotundus trace the large intestine after it has given off the caecum. The large 

 intestine beyond the caecum is named the colon. The colon is supported by a 

 part of the dorsal mesentery called the mesocolon. The first part of the colon, the 

 ascending colon, is rather long and pursues a winding course. At first its wall 

 bears three longitudinal muscular bands, the bands or taeniae of the colon. Be- 

 tween the taeniae the wall of the colon is greatly puckered, forming little saccula- 

 tions, the haustra. Beyond the ascending colon, the colon runs for a short 

 distance transversely across the peritoneal cavity from right to left and is then 

 named the transverse colon. At the left it turns abruptly posteriorly as the de- 

 scending colon. At this turn the mesocolon is fused to the mesogaster. The 

 descending colon passes straight posteriorly and disappears dorsal to the uro- 

 genital organs. 



Cat: The junction of small and large intestine is marked by a slight pro- 

 jection, the caecum, a vermiform appendix being practically absent. The large 

 intestine or colon passes forward as the ascending colon; then turns and extends 

 across the peritoneal cavity from right to left as the transverse colon ; and turns 

 abruptly at the left and proceeds straight posteriorly as the descending colon. 

 The mesentery of the colon is named the mesocolon. At the left where the 



