THE ESSENTIAL PHENOMENA OF DIGESTION. 35 



the cardiac, the stomach is a continuation of the cesopha- 

 gus ; by its lower orifice, the pylorus, it communicates 

 with the small intestine. Its mucous membrane secretes 

 an acid liquid, which is a very active agent in digestion, 

 and is called the gastric juice. 



The small intestine is a smooth, thin, and narrow tube, 



Fio. 20. 



Small intestine 



POSITION OF THE PRINCIPAL ORGANS OF DIGESTION. 



having an average length of five or six yards, and form- 

 ing a large number of coils, which occupy a large portion 

 of the abdominal cavity. At close intervals its mucous 

 membrane forms folds, called eonnivent valves, whose 



