XXX VII I. Gastric digestion. 



/. Materials. -Two fresh pig-stomach's; ^ Ko. clean sea 

 sand; 4 eggs; fibrin; bread; milk; jellied gelatin; casein; 

 rennin. 



2. Preparation. 



( 1 ) To prepare artificial gastric juice. 



(a) Stretch a fresh stomach of a pig upon a board 

 with mucous surface up; fix with nails. 



() Rinse off the mucous membrane gently with cold 

 water. 



(V) Scrape thoroughly with a dull edged table knife, 

 or an equivalent; collect the scrapings in a large 

 mortar. 



(dT) Grind the scrapings in clean, fine sand. 



(/) Add an equal volume of 0.2% HC1 and leave for 

 24-48 hours, stirring occasionally. 



(/) Strain through linen; filter, and preserve in a glass 

 stoppered bottle. Label: Acidulated aqueous extract 

 of pepsin. 



() For use dilute this extract with three or four vol- 

 umes of 0.1% HC1 (App. A-17). Label: Artificial 

 gastric juice (1). 



(2) To prepare a glycerin extract of pepsin. 



(a) Rinse off the mucous membrane of a fresh pig- 

 stomach with cold water and remove the mucous 

 membrane from the muscular walls of the stomach. 



() Grind the mucous membrane in the meat hasher. 



(/) Put the hashed tissue into a beaker and cover 

 with two volumes of pure glycerin. Stir the mix- 



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