CHEMICAL PHENOMENA OF DIGESTION. . 143 
chloric acid from the chlorides. Following up the compari- 
son between the two acids, we have recognized in the acid 
of gastric juice all the characters pointed out by M. Pelouze 
for lactic acid; these two acids give in reality salts of lime, 
baryta, zinc, and copper soluble in water ; a salt of copper 
which forms with lime a soluble double salt the colour of 
which is deeper than that of the simple ; a salt of lime solu- 
ble in alcohol and precipitated from its alcoholic solution by 
ether. Upon the whole, from the characters enumerated, 
the existence of this acid appears to us, at present, incon- 
testable. Mr. Chevreul and Messrs. Leuret and Lassaigne 
have already designated lactic acid in gastric juice. 
Conclusions. From the preceding facts it may be asert- 
ed that the acid re-action of gastric juice is not owing to 
biphosphate of lime, but, on the contrary, results from an 
acid in a free state in the gastric fluid. We never could 
prove the existence of free hydrochloric and acetic acids 
as had been indicated. We have constantly found charac- 
ters very distinct from lactic acid united to a feeble propor- 
tion of phosphoric acid.* According to us lactic acid should 
be considered as a constant physiological production of 
organism. Whatever in fact be the conditions of alimenta- 
tion in which we place the animals, we have never seen 
the acid principle of gastric juice differ in its nature. So 
that after an exclusive vegetable or animal diet kept up for 
several days, or even after a prolonged diet, we have always 
found free lactic acid. 
In asserting that lactic acid is the constant cause of the 
acidity of gastric juice, we do not wish to create the belief 
that this acid by its nature is endowed with certain special 
properties which render it indispensable to the action of the 
phenomena of digestion. On the contrary, it results from 
* The phosphoric acid we signalize here, should be looked upon as a secon- 
dary product of a re-action of lactic acid upon the phosphate contained in the 
gastric juice. 
