Till r. II MICAL PBO( OP DIG1 STION 



siderable quantity 0.05 per cenl or more of an organic acid is nee 

 sary, whereas it requires only a trace of hydrochloric acid. Normal 

 human gastric juice, when titrated with one of these indicators, gi 

 a figure which corresponds to aboul 0.03 N hydrochloric acid (see pi 



22 . For the accurate determination of the hydrogen-i ioncentration, 



it is necessary to use the gas-chain method (see page 29 . 



When gastric juice is collected through a fistula from an empty 

 stomach, very little difference will be found between the free hydro- 

 chloric acid and the total acid; thai is, between the results obtained by 

 the sec. .ml and the firsl of the methods described above. This is- because 

 in such juice there is no organic matter capable of combining with the 

 hydrochloric acid, and there are no other acids, such as lactic or butyric, 

 which might l>e produced by fermentative processes The differei 

 between the two titrations, however, becomes quite marked when pro- 

 tein food is undergoing digestion in the stomach, because at its different 

 stages of digestion protein combines with increasing quantities of the 

 hydrochloric acid. The pathologic condition in which there is most 

 definitely a diminution of the hydrochloric acid is cancer, either of the 

 stomach itself or occasionally of some other part of the body. An in- 

 crease is particularly marked in ulcer of the stomach. A considerable 

 variation in hydrochloric acid may however be the resull merely of func- 

 tional (neurotic) conditions. 



The Soubce of the Acid 



A question that lias puzzled physiologists for many years concerns thr 

 mechanism l>n which hydrochloric acid is secreted. The percentage of 

 hydrochloric acid in the gastric juice is considerably above that at which 

 any animal cells can live, and ye1 this acid is secrete. I by the lining 

 membrane of the stomach, its source being, of course, the Bodium 

 chloride of the blood plasma. Bow then do the cells of the gastric 

 glands bring aboul the separation of this powerful acid from tl 



fectly neutral bl 1 plasmal In the first place, it is significant thai the 



mucous membrane of the Btomach contains a higher p< of 



chlorine than the average of other organs and tissues, indicating that it 

 has the power "t' abstracting chlorine from the blood. The ei 

 chlorine in the mucosa must, moreover, he hut a very small fraction of 

 that actually secreted into the the gastric juice. The chlorine content 



of the mucosa of the cardiac end is considerably greater than that of the 

 pyloric. These facta indicate that chlorine is attracted by the gastric 

 cells, bui they throw no light on the question as to where the hydro- 

 chloric acid is really forme, I. Is it in the cells, or only in the hum ■ 

 the gland tubes.' That is to say, is it formed b< after the gastric 



