224 



UNCONSCIOUS NERVOUS OPERATIONS 



porting membrane for the intestine, called the mesentery. 



This is gathered up and connected with the wall of the 



abdominal cavity near the spinal 

 column. The blood vessels and 

 nerves pass through the mesen- 

 tery to reach the intestine, and 

 the absorbents also pass through 

 it from the intestine. The two 

 layers of muscular fibers, one 

 circular and one longitudinal, 

 in the intestinal wall, are of the 

 unstriped, involuntary kind. 



316. Nerves of the Small Intes- 

 tine. Between the muscular 

 layers is a plexus of nerve fibers 



W ^ ] lnan y ganglia ;i 11( l i ]l tin; 

 layer beneath the mucous mem- 

 brane of the lining is another 

 nerve plexus, also gangliated. 



317. The Mucous Membrane of 

 the Small Intestine has a very 

 important part in the function 

 of digestion, and is of peculiar 

 structure. Like the lining mem- 

 brane of the stomach, it has an 

 inner layer of columnar epithe- 

 lium, but unlike that of the 

 stomach the lining of the intes- 

 tine is for a large part of its 

 length laid in folds which do 

 not disappear when the canal is 



are called valvulce conniventes 

 (Fig. 110). They lie around the inner surface of the 



Fig. 111. The stomach and 

 intestines. 



1 stomach. 



2 duodenum. 



3 small intestine. 



4 termination of the ileum. 



5 caecum. 



<5 vermiform appendix. 



7 ascending colon. 



8 transverse colon. 



9 descending colon. 



10 sigmoid flexure of the colon. 



11 rectum. 



12 spleen. 



13 anus. 



distended. These folds 



