[_Transient heat dispart_. l. 401. Dr. Crawford in his ingenious work on
animal heat has endeavoured to prove, that during the combination of the
pure part of the atmosphere with the phlogistic part of the blood, that
much of the matter of the heat is given out from the air; and that this
is the great and perpetual source of the heat of animals; to which we
may add that the phosphoric acid is probably produced by this
combination; by which acid the colour of the blood is changed in the
lungs from a deep crimson to a bright scarlet. There seems to be however
another source of animal heat, though of a similar nature; and that is
from the chemical combinations produced in all the glands; since by
whatever cause any glandular secretion is increased, as by friction or
topical imflammation, the heat of that part becomes increased at the
same time; thus after the hands have been for a time immersed in snow,
on coming into a warm room, they become red and hot, without any
increased pulmonary action. BESIDES THIS there would seem to be another
material received from the air by respiration; which is so necessary to
life, that the embryon must learn to breathe almost within a minute
after
its birth, or it dies. The perpetual necessity of breathing shews, that
the material thus acquired is perpetually consuming or escaping, and on
that account requires perpetual renovation. Perhaps the spirit of
animation itself is thus acquired from the atmosphere, which if it be
supposed to be finer or more subtle than the electric matter, could not
long be retained in our bodies, and must therefore require perpetual
renovation.]


"Thus when the Egg of Night, on Chaos hurl'd,