524 
EXPERIMENTS ON DIGESTION. 
into the intestinal canal, to the end that the portions which are not 
yet dissolved shall be more fully exposed to the action of the 
gastric juice. 
The functions of the stomach, relative as well to nutrition, se- 
cretion, and its sensibility to and susceptibility of irritation, and also 
to the movements or phenomena of irritability, appertain to it only 
so long as it is in connexion with and has relation to the rest of 
the living organism; it therefore depends on the circulation of the 
blood, and the influence of the nervous system. 
The arterial blood is the fluid by which the stomach is nou- 
rished, and at the expense of which the gastric juice is formed : 
every circumstance therefore which has influence on the formation 
or production of blood, or the conversion of arterial into venous 
blood, ought to be considered, as well as those which bear imme- 
diately on the function of digestion. Deficiency of nourishment, 
a great loss of blood, or an augmentation of the secretion of va- 
rious fluids, weaken the digestion, because the}' diminish the nu- 
trition of the stomach and its secretory power, and also diminish the 
power of its muscular parietes, and restrain the vital influence 
which the nervous system exercises upon it. Every thing which 
disturbs the respiration, whether it be by rendering difficult, or 
suspending the respiratory movements, or introducing impure or 
vitiated air, or impeding the circulation of the blood through the 
lungs, or, finally, injuring the normal structure of the lungs, all 
enfeeble the digestion, because the blood no longer possesses the 
property of fully maintaining the nutrition and vitality of the 
stomach, or furnishing it with the materials for the supply of 
gastric juice, abundant in quantity and efficacious. The heart 
and the arteries exercise an essential influence on digestion, by 
conducting to the parietes of the stomach the blood which is ne- 
cessary for its nutrition, and the secretion of the gastric juice, 
and the manifestation of the phenomena of irritability and sen- 
sibility. 
Finally, as to the influence of the nervous system on the digest- 
ive function, there cannot be a moment’s doubt of it, although it 
may be difficult to explain the precise connexion between them. 
The stomach receives numerous and large nervous branches, as 
well from the par vagum as from the great sympathetic. The 
first form large plexuses on the oesophagus, and send a multitude 
of branches to the muscular and vascular tunics of this organ : 
the others surround, with the most complicated and delicate net- 
work, the arteries which supply the stomach, and distribute them- 
selves over all the tunics of that viscus. 
The united experiments of the best physiologists lead to the 
following conclusions : — 
