d to show, that a strict connexion exists
between the reception of oxygen into the body, and the vital
principle.

When an animal has been killed by depriving it of oxygen gas, the
heart and other muscles, and indeed the whole system, will be found
completely to have lost its excitability. This is not the case when
an animal is killed in a different manner. When an animal is shot, or
killed in the common manner, by bleeding to death, if the heart be
taken out, it will contract for some hours, on the application of
stimulants. But this is not the case with an animal that has been
drowned, or killed by immersion in carbonic acid, azotic, or
hydrogenous gases; in these last instances, the heart either does not
contract at all, or very feebly, on the application of the strongest
stimulants.

We have already seen that oxygen unites with the blood in the lungs,
during respiration: by the circulation of the blood it is distributed
to every part of the system, and we shall find, that in proportion to
its abundance is the excitability of the body. In proof of this, I
shall relate some facts and experiments.

Dr. Girtanner injected a quantity of very pure oxygen gas into the
jugular vein of a dog: the animal raised terrible outcries, breathed
very quickly, and with great difficulty: by little and little his
limbs became hard and stiff, he fell asleep, and died in the course
of a few minutes afterwards. It ought here to be observed, that any
of the gases, or almost any fluid, however mild, when thus suddenly
introduced into the circulating system, generally, and speedily,
occasions death.

On opening the chest, the heart was found more irritable than
ordinary, and its external contractions and dilatations continued for
more than an hour: the right auricle of the heart, which usually
contains black venous blood, contained, as well as the right
ventricle, a quantity of blood of a bright vermilion colour; and all
the muscles of the body were found to be more than usually irritable.
This experiment not only proves that the vermilion colour of the
blood proceeds from oxygen, but likewise seems to show, that oxygen
is the cause of excitability.

A quantity of azotic gas, which had been exposed for some time to the
contact of lime water, in order to separate any carbonic acid gas it
might contain, was injected into the jugular vein of a dog. The
animal died in twenty seconds. Upon opening the chest, the heart was
found filled wit