THE ACID OF THE GASTRIC JUICE. 355 



97 per cent, of the base will be combined with the hydrochloric acid, and 

 3 per cent, with the acetic acid ; or, otherwise, 3 per cent, of the hydrochloric 

 acid will be free and 97 per cent, of the acetic acid, supposing that equivalent 

 quantities of the two acids are present. 1 Such a mixture would possess only 

 a slightly higher coefficient of distribution than acetic acid. But if the 

 sodium acetate be added to hydrochloric acid, already feebly combined with 

 something else, the power of the acid to combine with the sodium will be 

 diminished, on account of the tendency to remain combined with this sub- 

 stance, and the amount of hydrochloric acid uncombined with sodium will be 

 increased ; this will remain to a greater extent in the watery layer, and on 

 shaking with ether the coefficient of distribution will be much greater than 

 that of acetic acid. 



Richet found traces of leucine in the gastric mucous membrane^ and be- 

 lieves, mainly on this ground, that the hydrochloric acid of the gastric juice 

 is in combination with leucine. But there is no good reason for going so far 

 afield to seek a partner for the hydrochloric acid; any substance in combination 

 with the acid would produce such an effect as Richet obtained, and it is far 

 more probable that the hydrochloric acid is in combination with the albumoses 

 of the gastric juice than with leucine, especially as leucine has not been found 

 in gastric juice, and hydrochlorate of leucine does not act as an acid to pepsin, 

 as shown by the inability of a mixture of the two to digest proteids. 2 



This account of Eichet's work has been placed here on account of the bear- 

 ing of the latter part of it on the question of the combination of the hydro- 

 chloric acid, but the first part of it is also of great value in showing that pure 

 gastric juice is practically free from organic acid. 



Organic acids present during carbohydrate digestion. Although organic 

 acids are entirely absent in pure gastric juice, or at most are only present 

 in traces, this is by no means the case during digestion, especially of food 

 rich in carbohydrates. 



The food passing into the stomach during a meal is alkaline in 

 reaction, by reason of the saliva with which it is abundantly mixed ; and 

 in addition, during and after a meal a considerable quantity of saliva is 

 swallowed by itself. As Beaumont 3 and others have shown, there is no 

 secretion of acid gastric juice when the stomach is empty, and although 

 active secretion begins with the arrival of the first portions of food in 

 the stomach, some time must elapse before the alkaline reaction of the 

 masses of food and saliva is neutralised by the acid of the gastric juice, 

 and a reaction due to free hydrochloric acid established, after saturation 

 of the soluble proteid of the food. This interval is exceedingly difficult 

 to estimate, the delicate colour reactions for free hydrochloric acid being so 

 deceptive in a heterogeneous fluid like the contents of a stomach ; 

 van de Velden 4 states that it varies from half an hour to two hours, 

 and is on an average three-quarters of an hour. During this time con- 

 version of starch by ptyalin goes on, 5 and in addition bacterial action 

 begins with the production, from the carbohydrate part of the food, of 

 lactic acid, 6 accompanied by traces of butyric and acetic acids. 



1 J. Thomsen, " Thermochemische Untersuchungen," Ann. d. Phys. u. Chem., Leipzig, 

 1869-1871, Bde. cxxxviii.-cxliii. 



2 See Gamgee, "Physiological Chemistry," vol. ii. pp. 97-99. 



3 See article on " Mechanism of Gastric Secretion."' 



* Ztschr.f. physiol. Chem., Strassburg, 1878, Bd. ii. S. 205. 



fi See under " Ptyalin," p. 329. 



6 According to Maly, the greater part of the lactic acid is the ordinary lactic acid of 

 fermentation, but this is accompanied by a smaller quantity of sarcolactic acid, which may 

 occasionally be much increased in amount, Ber. d. deutsch. chem. Gesellsch., Berlin, 1874, 

 S. 156 ; Ann. d. Chem., Leipzig, 1874, Bd. clxxiii. S. 227. 



