scientific history a more striking example of
the fatal influence which incorrect but
fashionable doctrines are able to exert on the
intellect of a man of genius, even when armed
with important and well-founded observations.

The crowning discovery was reserved for
the great founder of modern chemisty,
Lavoisier. In seventeen hundred and seventy-
seven, he published his Experiments on the
Respiration of Animals. Under a bell-glass
filled with air, and whelmed over a basin of
mercury, he placed various small animals.
After their death, the air in the bell-glass
was found to have become unfit for
respiration; it no longer served to maintain
combustion; it contained carbonic acid, and less
oxygen than in its normal state. He thence
concluded that the respiration of animals
deprives the air of oxygen, produces no
modification in its azote, but replaces the oxygen
by a nearly equivalent volume of carbonic
acid. The same year he read before the
Academy of Sciences his famous memoir On
Combustion in General. He did not take
leave of the subject without applying his
doctrine to the explanation of the phenomena of
respiration; and he stated his theory of
animal heat, which was always uppermost in
his mind. The pure air (oxygen), he said,
which has entered the lungs, comes out of
them partly changed into fixed air (carbonic
acid). By the process, therefore, of passing
through the lungs, the pure air experiences a
decomposition analogous to that which takes
place during the combustion of charcoal.
Now, in the combustion of charcoal, there is
a disengagement of the matter of fire—of
caloric, or heat; consequently, there ought to
be also a disengagement of heat in the lungs
in the interval between an inspiration and
an expiration; and it is doubtless this matter
of fire distributed by the blood throughout
the animal economy, which maintains a
constant warmth of about thirty-two degrees
and a-half of Réaumur's thermometer. What
confirms the notion that animal heat depends
on the decomposition of air in the lungs, is
the fact that the only warm animals are
those which breathe frequently, and that this
warmth is proportionally greater according
as the respiration is more frequently
performed; that is to say, there is a constant
relation between the heat of the animal and
the quantity of air which enters, or, at
least, is converted into fixed air inside the
lungs. In short, an animal, a guinea-pig for
instance, burns in its lungs, in a given time,
a determinate quantity of carbon, furnished
by the venous blood; and this act of burning
produces an amount of heat which can be
measured, as we measure the amount of heat
that a bushel of coals will give out in a
furnace.

The identity of respiration and combustion
was thus established. The substance of the
animal itself, the blood, furnishes the
combustible; and as a lamp will go out if not
supplied with oil, so an animal will perish if
deprived of food wherewith to repair the
waste occasioned by the maintenance of its
vital warmth. It results, that the animal
machine is principally governed by three
main regulators: respiration, which
consumes hydrogen and carbon, and which
furnishes heat; perspiration, which increases
or diminishes, according as it is necessary
to carry off more or less heat from
the system; and lastly, digestion, which
restores to the blood what it has lost by
respiration and transpiration. Later on,
Lavoisier ascertained that, even with the
mammifers, the lung is not the only
respiratory surface; he discovered the cutaneous
respiration, and thus embraced, in their
combination, and to their full extent, the
relations which connect living beings with the
atmosphere. Spallanzani proved that the
absorption of oxygen is necessary to the
inferior animals; he showed that their skin
is a veritable respiratory organ; he even
demonstrated that, in frogs, the cutaneous
respiration is of more importance than the
pulmonary respiration, and is alone sufficient
to maintain the animal long in life. At the
same time, he proved that with the inferior
animals the absorption of oxygen is
accompanied by the disengagement of heat, the same
as in birds and mammifers. Dr. Franklin, we
know, writes enthusiastically of the effects of
air baths on his own proper person.

All the while that Lavoisier firmly
maintained his original idea, still he modestly
refrained from asserting that its details were
any other than provisional. The time
required to finish and perfect his great work
was not permitted to be his to enjoy. It
must be added that, about the same time,
Dr. Crawford, in England, occupied himself
in investigating the same subject, arriving at
nearly the same results. Edwards afterwards
proved the truth of Lagrange's
doctrine, that the combustion of the hydrogen
and the carbon of the blood is not effected in
the lungs, as Lavoisier supposed, but in the
circulating stream itself, and especially in
the capillaries, at the moment of the
transformation of arterial blood into venous blood.

A few general facts may be added apropos.
Infants are colder than adults. Women are
constitutionally less able to resist external
causes of cooling than men, and ought therefore
to be more guarded against accidents
from cold. The temperature of a sleeping
man is nearly a degree centigrade lower than
that of the same man awake. M. Chossat
made three hundred observations, half on
pigeons that were wide awake, and the
other half on the same birds fast asleep;
their temperature, like that of human beings,
was higher at noon than at midnight. These
results accord with the circumstance, well
known to medical men, that slumbering
persons cannot expose themselves, without
considerable risk, to temperatures which they