ny may be considered an average number? When is the
consumption of oxygen the greatest?

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485. Dr. Southwood Smith has lately performed a series of very
interesting experiments, from which he deduces the following general
results: "1st. The volume of air ordinarily present in the lungs is
about twelve pints. 2d. The volume of air received by the lungs at an
ordinary inspiration is one pint. 3d. The volume of air expelled from
the lungs at an ordinary expiration, is a little less than one pint.
4th. Of the volume of air received by the lungs at one inspiration,
only one fourth part is decomposed at one action of the heart. 5th.
The quantity of blood that flows to the lungs, to be acted upon by the
air at one action of the heart, is two ounces, and this is acted on in
less than one second of time. 6th. The quantity of blood in the whole
body of the human adult, is twenty-five pounds avoirdupois, or twenty
pints. 7th. In the mutual action that takes place between the air and
blood, every twenty-four hours, the air loses thirty-seven ounces of
oxygen, and the blood fourteen ounces of carbon."

486. Apparently, atmospheric air is a simple element. But chemical
analysis shows its composition to be oxygen and nitrogen, in the
proportion of twenty-one parts of the former, and about seventy-nine
of the latter. In addition, there is a small amount of vapor of water
and carbonic acid. The pressure of this invisible, elastic fluid upon
the body of an ordinary sized adult, is estimated to equal thirty-five
thousand pounds.

487. The principal substance of a vitiated character in the
dark-colored blood is carbonic acid. And since there is no chemical
affinity between the oxygen and nitrogen of the air, the former
readily unites with some of the elements of the blood. Hence, whenever
blood is presented to the air in the lungs, the oxygen leaves the
nitrogen, and becomes mixed with the circulating fluid. (Appendix J.)

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485. State the 1st, 2d, 3d, and 4th deductions from the experiments of
Dr. Southwood Smith. The 5th, 6th, and 7th. 486. Of what is
atmospheric air composed? What is the weight of air upon a common
sized man? 487. What is the principal substance of a vitiated
character in the dark-colored blood? What is said of the chemical
affinity between oxygen and nitrogen?

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488. Again, carbonic acid and water have a stronger affinity for
atm