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LXXIV. The Croonian Lecture, on some Physiolegical Re- 
searches respecting the Influence of the Brain on the 
Action of the Heart, and on the Generation of Animal 
. Heat. By Mr. B.C. Bropie, F.R.S.* 
Having bad the honour of being appointed, by the Pre- 
sident of the Royal Society, to give the Croonian Lecture, 
I trust that the following facts and observations will be 
considered as tending sufficiently to promote the objects for 
which the lecture was instituted. They appear to. throw 
some light on the mode in which the influence of the brain 
is necessary to rhe continuance of the action of the heart ; 
and on the effect which the changes produced on the blood 
10 respiration have on the heat of the animal body, 
In making experiments on animals to ascertain how far 
the influence of the brain is necessary-to the action of the. 
heart, J found that when an animal was pithed by dividing 
the spinal marrow in the upper part of the neck, respiration 
was immediately destroyed, but the heart still continued to 
contract circulating dark-coloured blood, and that in.some 
instances from ten to fifteen minutes elapsed before its ac- 
tion had entirely ceased. JT further found that when the 
head was removed, the divided blood-vessels being secured 
by a ligature, the circulation stil] continued, apparently un- 
affected by the entire separation of the brain. These ex- 
periments cenfirmed the observations of Mr. Cruikshankt 
and M. Bichat}, that the brain is not directly necessary to 
the action’of the heart, and that when the functions of the 
brain are destroyed,- the circulation ceases only in conse- 
quence of the suspension, of respiration. This Jed me to 
conclude, that, if respiration was produced artificially, the 
heart would continue to contract for a still Jonger period af 
time after the removal of the brain. The truth of this con- 
clusion was ascertained by the following experiment. 
Experiment 1.—Y divided the spinal marrow of a rabbit 
in the space between the occiput and atlas, and, having made 
an opening into the trachea, fitted into it a tube of elastic 
gum, to which was connected a small pair of bellows, so 
constructed that the Jungs might be inflated, and then al- 
lowed to empty themselves. By repeating this process once 
in five seconds, the lings being each time fully inflated with 
fresh atmospheric air, an artificial respiration was kept up. 
J then secured the blood-vessels in the neck, and removed 
** From Philosophical Transactions for 1811, Part I. 
+ Philosophical Transactions 1795. 
+ Recherches Physiologiques sur la Vie et la Mort, 
‘the 
