on the Influence of the Brain, &c 0 389 
quantity of air should be consumed by the blood passing 
through the lungs, when the functions of the brain, and those 
of the organs dependant on it, are suspended. Perhaps it is 
not unreasonable to suppose, that by pursuing this line of in- 
vestigation we may be enabled to arrive at some more precise 
knowledge respecting the nature of respiration, and the pur- 
poses which it answers in the animal economy. It would how- 
ever be foreign to the plan of the present communication to 
enter into any speculations on this subject, and I shall there- 
fore only remark, that the influence of the nervous system 
does not appear to be necessary to the production of the che- 
mical changes, which the blood undergoes in consequence of 
exposure to the air in the lungs.* 
* This conclusion is directly contrary to that deduced by M. Dupuytren, from 
a series of curious experiments, made with a view to ascertain the effects which follow 
the division of the nerves of the par vagum, and it is an object of some importance in 
the present investigation, to ascertain in what manner the apparently opposite facts, 
observed by M. Dupuytren and myself, are to be reconciled with each other. 
It was observed by this physiologist, that in an animal, in which both the nerves 
of the par vagum are divided, the blood returned from the lungs has a darker co- 
lour than natural, and that the animals, on whom this operation is performed, die 
sooner or later with symptoms of asphyxia, notwithstanding the air continues to enter 
the lungs ; and hence he concludes, that the changes which are produced on the blood 
in respiration are not the result of a mere chemical process, but are dependent on the 
nervous influence, and cease to take place when the communication between the lung* 
and the brain is destroyed. 
M. Provencal, in prosecuting this inquiry, ascertained that the animals subjected 
to this experiment give out less carbonic acid than before. 
M. Blainville observed, that the frequency of the inspirations is much dimi- 
nished ; and M. Dumas restored the scarlet colour of the arterial blood by artificially 
inflating the lungs, and from these and other circumstances, he has arrived at con- 
clusions very different from those ofM. Dupuytren. 
My own observations exactly correspond with those of M M. Dumas and Blain- 
viele. After the nerves of the par vagum are divided, a less quantity of carbonic 
MDCCCXII. g E 
