48 



DIGESTION. 



en, and in them are found granules which are supposed to be pepsin 

 or that from which pepsin is formed. 



FIG. 9 



Tubular Follicles, from pyloric portion of pig's stomach, showing their caecal extremities 

 and epithelial lining: at a the torn end of a follicle, showing its cavity more highly 

 magnified. 



What is the gastric juice ? 



When the stomach is not at work it contains no gastric juice, 

 but is bathed in an alkaline mucus. As soon as food enters the 

 organ, however, it immediately begins to secrete considerable quan- 

 tities of an acid fluid which soaks into and mingles with the food. 

 The celebrated case of Alexis St. Martin, who had a gunshot wound 

 resulting in gastric fistula, enabled Beaumont, surgeon U. S. A., to 

 investigate accurately its composition. It is a limpid, colorless fluid 

 of sp. gr. 1001-1010 and acid reaction. It contains about per cent, 

 solid matter. Its composition is nearly 



Water 99.50 



Pepsin 25 



Hydrochloric acid 05 



Salts (alkaline chlorides and phosphates) . . .20 



100.00 



This composition is not constant, as the proportions vary consider- 

 ably, HC1, for example, being present much more abundantly in 

 some cases. 



