LACTIC ACID THE NORMAL ACID OF THE STOMACH. 163 
ing acidity, and on heating the residue to thorough charring, 
and until all empyreumatic odour ceased to be given off, it was 
found that all acidity had disappeared. 
“ Experiment 6. — It was suggested that the acid reaction of 
the residuum might be due to phosphoric acid, and that it 
might have been decomposed by the heat employed and the 
carbon which was present. To determine this, another por- 
tion of the same fluid was mixed with three drops of a solution 
of phosphoric acid, and the mixture was carried through the 
same series of experiments, giving a successively increasing 
acidity, with this peculiar result, however — that even after 
the whole material had been thoroughly charred, as before, 
and still more highly heated, the acid reaction still remained, 
thus demonstrating that the acid detected in the product of 
digestion in the first experiments w T as not the phosphoric. 
te Experiment 7.— To ascertain whether hydrochloric acid, if 
present in the free state, could resist the distilling heat, and 
remain in the residuum w 7 hen concentrated, a minute drop was 
added to a quantity of water so large as to render its reaction 
undetectible by litmus ; and a like quantity to the fluid of 
digestion, and both were distilled. In both cases, a very 
distinct evidence of the presence of the acid was obtained in 
the distillate by a decided precipitate with nitrate of 
silver. 
Ci Experiments 6 and 7 go to show that the acid of the 
gastric juice, that at least upon which its most decided action 
depends, is not phosphoric acid, for it does not resist high 
heat, as that acid is known to do. It is probably not hydro- 
chloric, nor acetic, for these are both highly volatile, and are 
detected readily in the distillate by nitrate of silver. 
“Experiment 8. —This experiment was performed in verifi- 
cation of the doubt just stated, that hydrochloric acid is not 
present in the free state in the fluid of digestion. A portion 
of all the digestive fluids obtained from St. Martin, and a 
quantity vomited at will by another individual, were tested 
with pure deutoxide of manganese, without giving the slightest 
trace of the presence of chlorine. 
“ Another portion of the digestive fluids was carefully 
filtered, and a minute trace of chloride of calcium added to 
it; the material was then tested with oxalic acid, when im- 
mediately the white precipitate of oxalate of lime took place. 
Had any free hydrochloric acid been present, it would have 
prevented the appearance of the precipitate by dissolving it. 
To prove this, another portion of the same gastric fluid was 
filtered, and a minute quantity of hydrochloric acid and 
chloride of calcium were added to it. The addition of oxalic 
