3.20 



PHYSIOLOGY AND MORPHOLOGY OF ANIMALS. 



large on one side a little way from the end by a valve 

 (ileocsecal valve; Fig. 204). Each of these two parts are 

 again subdivided into three, as shown in the schedule: 



r Duodenum. ( Caecum. 



Small ■] Jejunum. Large j Colon. 



( Ileum. ( Rectum. 



The duodenum is the part next the stomach, seen in 

 Fig. 198, into which are poured the digestive juices 

 from the liver and pancreas. It is the largest and 

 shortest part of the small intestines, being about ten 

 inches long and two inches in diameter. The jejunum 

 and ileum grade completely into one another both in 

 structure and function. Of the large intestines, the 

 caecum is the somewhat enlarged blind extremity into 

 the side of which the ileum opens (Fig. 204) by the ileo- 

 cecal valve. Attached to the blind extremity there is 

 a curious, wormlike appendage, which by inflammation 

 gives rise to the grave disease (appendicitis) which is 

 now attracting so much attention. The rectum is the 

 last or lower part, about six inches long, and cylindrical 

 in form, opening through the anus. The colon is the 

 sacculated part between the cascum on the one hand 

 and the rectum on the other, and constitutes the prin- 

 cipal part of the large intestines. The caecum is in the 

 lower right-hand part of the abdomen. The colon runs 

 from it upward on the right side to the region of the 

 stomach, then across to the left, and then down the left 

 side to the rectum. 



Relations to the Abdominal Walls. — So long 

 and so slender a tube must be so held in place that it be 

 not tangled ; and also it must be in easy reach of the 

 great vessels which supply it with blood, and which take 

 away the digested food. This is done by a thin, trans- 

 parent membrane which is attached by one edge to the 



