l6o PHYSIOLOGICAL CHEMISTRY. 



To make the test for free hydrochloric acid, mix 5 cc. of this solution 

 with 5 cc. of the gastric filtrate and concentrate in a glass or porcelain 

 vessel on the water-bath. In presence of free hydrochloric acid the liquid 

 gradually becomes red as the concentration proceeds. 



BOAS' REAGENT FOR FREE HYDROCHLORIC ACID. 



Resorcinol 5 grams 



Cane sugar 3 grams 



Alcohol, 50 per cent 100 grams 



Add a few drops and evaporate as above. Color appears as in the 

 other test. 



Total Hydrochloric Acid. By the use of the above tests 

 the excess of hydrochloric acid beyond that which the proteins 

 and bases will hold is recognized. At one time this acid was 

 supposed to be all that could have any physiological value. 

 The importance of that combined with the proteins in the form 

 of acid albumin was not considered. From the explanations 

 given above it is evident that in some stages of the digestive 

 process the hydrochloric acid may be largely or wholly in 

 combination and therefore not in a form to be recognized 

 through the aid of the tests just given. From experiments 

 made under such conditions it would be wrong to conclude 

 that the stomach is secreting no acids. It has been found that 

 by making the test in a different way, employing phenol- 

 phthalein instead of the reagents mentioned above, the com- 

 bined acid may be readily recognized. To do this we must 

 make practically a quantitative analysis, and the method em- 

 ployed depends on the proper use of certain indicators. This 

 will be taken up presently. 



The Organic Acids. Under normal conditions, as already 

 stated, these are present in the stomach contents in very small 

 amounts only. As their formation depends on bacterial fer- 

 mentation processes, they appear only when hydrochloric acid 

 is absent, or present in relatively small proportion. Mineral 

 acids arrest bacterial fermentation quickly, from which it fol- 

 lows that in the healthy stomach there is never opportunity 

 for the accumulation of much lactic or other acid of like origin. 

 These acids are never products of secretion as is hydrochloric 



