82 THE GASTRIC JUICE. 



Others which are not so important, but the presence 

 of which may sometimes be significant, are for: 



1. Starch. 



2. Albuminous compounds. 



3. Eennin. 



4. Blood-coloring matters. 



Quantative tests are valuable in the cases of: 



1. Total acidity. 



2. Hydrochloric acid, free and combined. 



3. Organic acids. 



The reaction of normal gastric juice is, of course, acid. 

 In some pathological conditions it becomes neutral or alka- 

 line. Litmus-paper can be used for the test. 



To determine the total acidity of the juice filter it, 

 keeping it covered to prevent, as much as possible, evapora- 

 tion; then measure accurately 10 cubic centimeters with a 

 pipette and place it in a beaker. Add to this a few drops 

 of an alcoholic solution of phenol-phthalein, which serves 

 as an indicator to tell whether the liquid is acid or alkaline 

 during the determination, being red with alkalies and color- 

 less with acids. Then add slowly from a burette a solution 

 containing 4 grammes of sodium hydrate to the liter, stir- 

 ring continually, until the liquid is a faint pink color which 

 remains on standing a few minutes. Enough of the stand- 

 ard alkali has then been added to neutralize the acid sub- 

 stances present. Eead off this amount from the burette. 

 If no gastric juice is at hand, a solution for experimental 

 purposes can be made of a mixture of the above acids after 

 greatly diluting them. 



The acid phosphates may be normally present, but 

 cannot perform the functions of the hydrochloric acid in 



