168 SPECIAL PHYSIOLOGY 



juice has been successful the fibrin will dissolve in one or two minutes. 

 One may be certain that digestion is progressing rapidly, though 

 complete solution of the fibrin does not necessarily indicate complete 

 digestion of it; for complete digestion of a proteid implies that the 

 foodstuff is both dissolved and diffusible. The fibrin is dissolved; 

 it may or may not be diffusible. But this will be determined later. 



(5) To Determine the Active Factors of Gastric Digestion, (a) To 

 a few shreds of fibrin in a test-tube add a few cubic centimetres of 

 0.2 per cent. HC1. Carefully note results. Will dilute HC1 dissolve 

 fibrin ? Is it possible to digest a proteid without dissolving it ? 



(6) To fibrin add dilute neutral glycerin extract of pepsin. Is 

 solution effected? 



(c) To tube (a) add a few drops of the glycerin extract of pepsin. 



(d) To tube (6) add two volumes of 0.2 per cent. HC1. Note 

 results. Formulate conclusions. 



(6) To Determine whether the Acid Factor of Gastric Digestion 

 Need Necessarily Be Hydrochloric Acid. Prepare a 0.4 per cent, 

 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. 

 (VII) Malic acid. 



For each acid prepare four test-tubes as follows: 

 (a) Fibrin+1 c.c. glyc. ext. of pepsin+10 c.c. 0.4 per cent. acid. 



(6) Fibrin + 1 c.c. pepsin ext. + 10 c.c. 0.2 per cent. acid. 



(c) Fibrin+1 c.c. pepsin ext. + 10 c.c. 0.1 per cent. acid. 



(d) Fibrin+1 c.c. pepsin ext. + 10 c.c. 0.05 per cent. 

 Proceed in a similar manner with each acid. 



Tabulate results. May 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 is normally present in the stomach? 

 May any of the above acids serve as digestives and as foods? 



As digestives and as tonics? 



As digestives, foods, and tonics? 



Cite authorities. 



(7) To Determine the Optimum Strength of the Hydrochloric Acid. 

 Prepare with care the following three dilutions of hydrochloric acid: 

 10 per cent., 1 per cent., 0.1 per cent. 



Into twelve test-tubes put as many small masses of fibrin; into 

 each tube put 1 c.c. of neutral 10 per cent, dilution of glycerin extract 

 of pepsin. Label and fill the tubes as follows: 



Tube (a) 5 per cent.: Add to the fibrin 5 c.c. of 10 per cent. 

 HC1 and of distilled water a quantity sufficient to make 10 c.c. 



