236 HEALTH AND DISEASE 



pylorus, which is the strong muscular ring that separates the stomach 

 from the intestine, and it terminates at the point where the alimentary 

 canal suddenly enlarges to form the large intestine. Its length is more 

 than 70 feet, and its width, when undistended with food or gases, about 

 1| inch. It is suspended from the vertebral column by a double fold 

 of membrane (peritoneum), which is here named the mesentery. The 





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 Ml 



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>,? *^, 



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y 



• bands; <}, ileum, or terminal portion of small intestine: 

 ij, pelvic flexure; h, single colon 



/,/', large colon; 



blood-vessels, lacteals, and nerves of the intestine reach it by running 

 between these two layers of the mesentery. In structure the small in- 

 testine resembles the stomach in having an outer serous covering of 

 peritoneum, a middle layer of longitudinal and circular muscular fibres, 

 and an internal mucous layer. When closely examined the mucous mem- 

 brane of the small intestine exhibits a velvety or pile-like arrangement, 

 which is most conspicuous when the membrane is floating in water. This 

 appearance is due to the presence of an immense number of small jjro- 

 jections about ^ of an inch long, named villi (1, fig. 84), between which 

 are the openings of minute glands (Lieberkuhnian follicles), named after 

 Lieberkuhn, a Dutch anatomist, who first described them about 1745. 



