only dressed, but almost dry."

554. If a thermometer be placed under the tongue of a healthy person,
in all climates and seasons the temperature will be found nearly the
same. Sir Charles Blagden, "while in the heated room, breathed on a
thermometer, and the mercury sank several degrees; and when he expired
forcibly, the air felt cool as it passed through the nostrils, though
it was scorching hot when it entered them in inspiration."

_Observation._ Did not the human body possess within itself the power
of generating and removing heat, so as to maintain nearly an equality
of temperature, the most fatal consequences would ensue. In northern
latitudes, especially, in severe weather of winter, the blood would be
converted into a solid mass, and on the other hand, the fatty
secretion, when subjected to equatorial heat, would become fluid, and
life would be extinguished.

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What is related of Chantrey? Of Chaubert? Of Sir Charles Blagden? 553.
Give Sir Charles's own statement. 554. What is said of the temperature
of the human tongue? Mention the experiment by Sir Charles Blagden.
What would be the effect if the human system did not maintain an
equality of temperature?

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555. To enable man, and other warm-blooded animals, to maintain this
equilibrium of temperature under such extremes of heat and cold,
naturally suggests two inquiries: 1st. By what organs is animal heat
generated? 2d. By what means is its uniformity maintained?

556. The ancients had no well-arranged theory on the subject of animal
heat. They believed that the chief object of respiration was to cool
the blood, and that the heart was the great furnace where all the heat
was generated. At a later period, Mayow, from his discoveries
respecting respiration, asserted that the object of respiration was to
produce heat, and denied that the blood was cooled in the lungs.

557. When it was discovered that, both in combustion and respiration,
carbonic acid was produced and oxygen absorbed, it led Dr. Black to
conclude that breathing was a kind of combustion by which all the heat
of the body was produced. This theory was objected to, because, if all
the heat was generated in the lungs, like those parts of a stove in
contact with the fuel, they would be at a higher temperature than
those parts at a distance, which was known not to exist.

558. The next theory, and one which received the sanction of the
sci