DIGESTION AND ABSORPTION. 173 



possible to digest a proteid without dissolving it? 

 () To fibrin add dilute neutral glycerin extract of 



pepsin. Is solution affected ? 



(r) To tube (a) add a few drops of the glycerin extract 

 of pepsin. 



To tube (b) add 2 volumes of 0.2% HC1. 

 Note results. 



(X) Formulate conclusions. 



) To determine whether the acid factor of gastric diges- 

 tion need necessarily be hydrochloric acid. 



Prepare a 0.4% solution of each of the following 

 acids: 



(I) Lactic acid. 



(II) Sulphuric acid. 



(III) Nitric acid. 



(IV) Phosphoric acid. 



(V) Citric acid. 



(VI) Acetic acid. 



For each acid prepare four test tubes as follows: 

 (I) Lactic acid. 



(#) Fibrin -f- 1 c. c. glyc. ext. of pepsin -{- 10 c. c. 



0.4% acid. 

 () Fibrin -j- 1 c. c. pepsin ext. -|- 10 c. c. 0.2% 



acid. 

 (c) Fibrin -f- 1 c. c. pepsin ext. -j- 10 c. c. 01% 



acid. 

 (^/) Fibrin -f- 1 c. c. pepsin ext. -f- 10 c. c. 0.05% 



acid. 



Proceed in a similar manner with each acid. 

 Tabulate results. May any other acid or acids 

 take the place of HC1 as a factor in digestion ? 

 If so, in what minimum strength? Which one of 

 the above acids may be normally present in the 



