286 
EXPERIMENTS ON DIGESTION. 
physiologists have published opinions so little in accordance with ; 
each other, and, even, so contradictory as the gastric juice. Some 
have maintained that it is acid — others that it is alkaline — and 
others that it is neither the one nor the other. Some of the most 
celebrated chemists of the age have not dared to give any opinion 
with regard to it, and have frankly avowed their ignorance of 
every thing that concerns the history of this all-important fluid. 
The result of our experiments is, that the small quantity of fluid 
which we have found in the unirritated stomach of the dog and the 
horse when fasting is almost of a neutral character, or only very 
feebly acid ; but that, when the stomach has been irritated by 
pebbles or by pepper, the gastric juice — much more abundant — con- 
tains a free acid, and reddens the tincture of turnsol. Yiridet, 
Carminati, Baugnatelli, Werner, &c. have also ascertained that 
the gastric fluid of the mammalia is generally acid : Yiridet found it 
so in the stomachs of dogs, cats, rabbits, hares, hedgehogs, and pigs. 
Carminati observed that it was neutral in dogs and cats while 
fasting, but that, when these animals had eaten, this fluid reddened 
the turnsol. He also found the gastric juice of the pig to be acid. 
Baugnatelli remarked that it was acid in dogs and cats. Werner 
recognized the same state of the gastric juice not only in these 
animals but in the rabbit and the horse. 
That which plainly indicates the existence of a free acid in the 
gastric juice is the coagulation of milk by this liquid, not only in 
the stomach of the living animal, but even after death. Almost 
every experimentalist, who has concerned himself with this subject, 
has recognized this phenomenon. Littre killed two young dogs 
while they were in the act of sucking, and he found the milk in 
their stomachs coagulated. He with good reason attributed this 
coagulation to the action of the gastric juice. Spallanzani acknow- 
ledged this power of coagulation, and observed that the internal 
membrane of the stomachs of these animals possessed it for a con- 
siderable period after death. John Hunter had also observed the 
coagulation of milk in the stomach and out of it, by means of this 
fluid. Carminati coagulated milk by means of the gastric juice of 
a pig, and Everard Home pretended to have observed it only in 
the neighbourhood of the pylorus, where the secretory glands 
were most numerous. 
We have constantly remarked this property, and that not only 
about the pyloric orifice of the stomach but the cardiac. The co- 
agulation was always effected in a rapid and decisive manner, when 
gastric juice from the stomach of an animal that had been com- 
pelled to swallow pepper was poured on the milk. 
Although it is no longer possible to deny the existence of a free 
acid in the gastric juice of mammalia, chemists have not yet deter- 
mined the nature of that acid. Some have supposed it to be of a 
