* 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 imflam∣mation, 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 breath almost within a minute after its birth, or it dies. The perpetual necessity of breathing shews, that the material thus acquired is per∣petually consuming or escaping, and on that account requires perpetual renovation. Per∣haps 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.
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