EXPERIMENTS ON DIGESTION. 367 
The viscus then resumed the state of universal contraction by 
which it is characterized when empty. 
Some physiologists, as Pitcairn, Senec, Hecquet, and others, at- 
taching very great importance to the movements of the living 
stomach, have maintained that the aliment is, by means of these 
movements, broken down and comminuted, and converted into a 
pultaceous mass : but the experiments of Reaumur and Spallanzani 
on several of the mammalia have completely refuted this erroneous 
theory. Reaumur proved that digestion in the stomach of the dog 
was not accomplished by trituration, by making the animal swal- 
low fragile and compressible tubes filled with food, the sides of the 
tubes being pierced by numerous small holes. The form of the 
tubes did not undergo the slightest alteration in the stomach, but 
the food which they contained was completely dissolved. Spallan- 
zani performed the same experiments, and with a similar result. 
The augmented Secretion of the Gastric Juice. 
Having reached the stomach, and come into contact with its 
mucous membrane, the aliment has an exciting influence upon it, by 
means both of its mass and its chemical properties. It thence re- 
sults that the arterial blood now flows in a larger stream into the vas- 
cular tissue of this membrane than when the animal is fasting and 
the membrane unexcited, and a red tinge begins to appear. At the 
same time the gastric juice is secreted more abundantly, and appears 
in the form of a greyish white fluid, a little clouded and mixed with 
mucous flocculi. When, in its empty state, and no agent exerts its in- 
fluence upon the stomach, its walls are scarcely moistened ; but when 
it is stimulated either mechanically or chemically, a copious secre- 
tion of the gastric juice ensues. The quantity of the gastric juice 
secreted during the process of digestion appears to depend on the 
degree of excitation produced by the aliment. We have found 
most of this fluid in animals that had eaten bones, cartilage, fibrine, 
cheese, butter, the white of an egg boiled, gluten, flesh, and bread ; 
and less in those to whom substances mild and easy of digestion 
had been given, as gelatine, gum, starch, &c. The quantity of the 
gastric juice is then proportionate to the digestibility and dissolubi- 
lity of the alimentary substances. More is formed after the use of 
food difficult to dissolve and to digest, than after that which is 
more susceptible of solution and digestion; in other words, the 
former produce a stronger and more prolonged excitation than the 
latter. - 
The Acidity of the Gastric Juice. 
The food, of whatever nature it may be, becomes acid and red- 
dens the tincture of turnsol after it has been penetrated by the 
