From Galileo to Newton by A. Rupert Hall

Author:A. Rupert Hall [Hall, A. Rupert]
Language: eng
Format: epub
Tags: science, Physics, Astrophysics, history, Biography & Autobiography, Science & Technology
ISBN: 9780486150253
Google: dGe0I_YJuScC
Publisher: Courier Corporation
Published: 2012-07-06T00:19:51.475536+00:00

Before this, experiments plausibly evincing the necessity of air for life and combustion had been performed at Oxford in the late 1650s by Robert Boyle and reported in his New Experiments Physico-Mechanicall, Touching the Spring of the Air, and its Effects (1660). With the first of all laboratory vacuum-pumps he showed that a small animal and a flame expired equally quickly as the air was withdrawn from the receiver, although attempts to discover whether or not the animal would outlive a flame enclosed with it in air proved inconclusive. Nor did it prove possible to prove decisively that nitre in vacuo would support combustion, as gunpowder would burn under water. However, the absence of any change of pressure when a flame or an animal expired in a closed space was demonstrated, so that clearly the available air had not simply been used up. Nor did it seem that either was stifled by its own exhalations.

None of this experiment or speculation threw much light on the physiology of respiration, which was investigated in further experiments by the Royal Society. In one (formerly performed by Vesalius) Hooke in 1667 cut open the thorax of a dog so that the lungs collapsed; the unfortunate animal was then kept alive by blowing air into them with a bellows. Upon Ent remarking that this showed only what respiration was not—“that the lungs did not serve to promote by their agitation the motion of the blood ”—Hooke stated the positive (but mistaken) conclusion that the respiration discharged“the fumes of the blood”.27 Hooke’s was indeed an odd opinion for one who had addressed himself seriously to the problem of combustion and studied the effect of access to air on flames. At this point it was necessary to make more precise experiments on the long-suffering animals, which Richard Lower described in his Tractatus de Corde (“Treatise on the Heart”, 1669). Lower went straight to the key question—the long known difference in colour between venous and arterial blood. Suspecting that the change took place in the lungs, he blocked the trachea of a dog and found that blood drawn from the cervical artery was as dark as that in the adjacent jugular vein. Borrowing Hooke’s technique he blew into the lungs with bellows while blood was forced through them from the vena cava; it issued from the pulmonary vein with the bright, florid appearance of arterial blood. Moreover:

That this red colour is entirely due to the penetration of particles of air into the blood is quite clear from the fact that, while the blood becomes red throughout its mass in the lungs (because the air diffuses in them through all the particles, and hence becomes thoroughly mixed with the blood), when venous blood is collected in a vessel its surface takes on this scarlet colour from exposure to the air.28

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