234 HUMAN ANATOMY. 



The areolar or submucous coat connects the muscular with 

 the mucous coat; 



The mucous coat is thinner and redder than that of the 

 stomach, and is thrown into numerous transverse folds the 

 valvulae conniventes most numerous in the upper part; they 

 diminish as it descends and finally disappear in the ileum. They 

 increase the secreting and absorbing surface of the mucous mem- 

 brane and retard the passage of the food. 



The mucous membrane also contains the villi and four kinds 

 of glands: 



Simple follicles, or crypts of Lieberkiihn; 

 Duodenal glands, or Brunner's glands; 

 Solitary glands; 

 Agminate, or Peyer's glands. 



The villi are minute vascular projections of the mucous 

 membrane scattered throughout the surface of the small intes- 

 tine. Their structure consists of a pouchlike termination of a 

 lacteal in the centre surrounded by a minute plexus of capillary 

 vessels inclosed in a basement membrane and covered with co- 

 lumnar epithelium. 



The simple follicles, or crypts of Lieberkfthn, are scattered 

 throughout the mucous membrane of the entire small intestine. 

 They consist of minute tubes of basement membrane, lined with 

 columnar epithelium and surrounded by a capillary net-work. 



The duodenal or Brunner's glands are distributed to the 

 duodenum and jejunum only. They are largest and most numer- 

 ous in the vicinity of the pylorus. They are composed of tubular 

 alveoli, lined by epithelium, and having a small duct opening 

 on the mucous membrane. 



The solitary glands are distributed throughout the small 

 intestine, being most numerous in the last portion of the ileum. 

 They consist of lymph follicles, and communicate with the lac- 

 teal system by means of lymph spaces. 



Peyer's glands, or Peyer's patches, consist of an aggrega- 

 tion of the solitary glands into oval groups of twenty or thirty 

 along the small intestine at a point opposite the attachment 

 of the mesentery. The patches are about fifteen to thirty in 

 number, each measuring about one-half to two inches in length 

 and one-half inch in breadth. Their axes are parallel with the 

 length of the intestine. In the duodenum they are few and 

 small in size, and the mucous membrane of the valvulae conni- 

 ventes over them is reduced in size and much distorted. 



The arteries are derived from the pyloric, pancreatico- 

 duodenal, and superior mesenteric. They reach the intestines 



