EXAMINATION OF THE GASTRIC CONTENTS. 487 



Under pathological conditions irregularities in the secretion may 

 occur. The quantity of enzymes may be diminished and both enzymes 

 or, as found in certain cases, one (the rennin), may be absent. The 

 hydrochloric acid may also be absent or may exist in very small amounts. 

 A pathological high degree of acidity of the pure juice is not very prob- 

 able, while on the contrary a hypersecretion of gastric juice in different 

 forms does occur. 



In testing the gastric juice or the filtered stomach contents, diluted 

 with digestive hydrochloric acid, for pepsin, we make use of the pepsin 

 tests given on pages 469, 470. In testing for rennin the liquid must be 

 first carefully neutralized, and 1-2 cc. of this liquid added to 10 cc. 

 milk. In the presence of appreciable quantities of rennin, the milk 

 should coagulate at room temperature within 10-20 minutes without 

 changing its reaction. The addition of lime salts is unnecessary, and 

 may readily lead to erroneous conclusions. 



In many cases it is especially important to determine the degree of 

 acidity of the gastric juice. This may be done by the ordinary titration 

 methods. Phenolphthalein must not be used as an indicator, as too 

 high results are produced in the presence of large quantities of proteins. 

 Good results may be obtained, on the contrary, by using very delicate 

 litmus paper. Although the acid reaction of the contents of the stomach 

 may be caused simultaneously by several acids, still the degree of acidity 

 is here, as in other cases, expressed in only one acid, e.g., HC1. Gen- 

 erally the acidity is designated by the number of cubic centimeters of 

 N/10 sodium hydroxide required to neutralize the several acids in 

 100 cc. of the liquid of the stomach. An acidity of 43 per cent means 

 that 100 cc. of the liquid of the stomach required 43 cc. of N/10 sodium 

 hydroxide to neutralize it. 



It is also important to be able to ascertain the nature of the acid or 

 acids occurring in the contents of the stomach. For this purpose, and 

 especially for the detection of free hydrochloric acid, a great number of color 

 reactions have been proposed which are all based upon the fact that the 

 coloring substance gives a characteristic color with very small quanti- 

 ties of hydrochloric acid, while lactic acid and the other organic acids 

 do not give these colorations, or only in a certain concentration, which 

 can -hardly exist in the contents of the stomach. These reagents are a 

 mixture of FERRIC-ACETATE and POTASSIUM-SULPHOCYANIDE solutions 

 (MOHR'S reagent has been modified by several investigators), METHYL- 

 ANILINE-VIOLET, TROP^JOLIN 00, CONGO RED, MALACHITE-GREEN, PHLORO- 



GLUCINOL-VANILLIN, DiMETHYLAMiNOAZOBENZENE, and others. As reagents 

 for free lactic acid, UFFELMANN suggests a strongly diluted, amethyst-blue 

 solution of FERRIC CHLORIDE and CARBOLIC ACID, or a strongly diluted 

 nearly colorless solution of FERRIC CHLORIDE. These give a yellow 

 color with lactic acid, but not with hydrochloric acid or with volatile 

 fatty acids. 



The value of these reagents in testing for free hydrochloric acid or lactic 

 acid is still disputed. Among the reagents for free hydrochloric acid it seems 

 STEENSMA'S l modification of GUNZBURG'S test with phloroglucinol-vanillm, and 



1 Bioeh. Zeitschrift, 8. 



