THE ACID OF THE GASTRIC JUICE. 355 
[)7 per cent, of the base will be combined with the hydrochloric acid, and 
3 per cent, with the acetic acid ; or, otherwise, •'> per cent, of the hydrochloric 
acid will be free and 97 per cent, of the acetic arid, 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 arid to combine with the .sodium will be 
diminished, on account of the tendency to remain combined with tins 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. 
Bichet 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 Bichet 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 Bichet'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 Yelden 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. C'hcm., Leipzig, 
1869-1871, Bde. cxxxviii.-cxliii. 
2 See Gamgee, "Physiological Chemistry," vol. ii. pp. 97-99. 
3 See article on "Mechanism of Gastric Secretion." 
4 Ztschr. f. physiol. Chem., Strassburg, 1878, Bd. ii. S. 205. 
5 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, Bcr. d. deutsch. chem. Gcsellsch.. Berlin, 1871, 
S. 156 ; Ann. d. Chem., Leipzig, 1874, Bd. clxxiii. S. 227. 
