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With the Author's Compliments.

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A LECTURE

COURSE OF LECTURES

MEDICAL CLASS IN YALE COLLEGE.

DELIVERED SEPTEMBER 14, 1871,

PROF. B. SILLIMAN, M.D.

PRINTED BY CHARLES C. CHATFIELD & CO.

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NEW HAVEN, CONN.:
PRINTED BY CHARLES C. CHATFIELD & CO.

40057

MCB
Si3

BOSTON MEDICAL LIBRARY
IN THE

FRANCIS A. COUNTWAY
LIBRARY OF MEDICINE

LECTURE.

A century has now nearly passed since on August Ist, 1774, Dr. Priestley first recognized the distinctive properties of oxygen gas which he called "dephlogisticated air." Lavoisier in the same year and shortly after the discovery of oxygen by Priestley, published a memoir in which he showed that in common combustion and in the calcining of metals it was not the whole of the air but only one part of it which was active in producing these changes. He at first called the active portion of the air "vital air," or "air eminently adapted for supporting combustion and respiration." Up to this time chemists had distinguished what we now call metallic oxides as the "calx" of metals. Lavoisier in preparing oxygen from what was then called "mercurial calx" (mercuric oxide, or "red precipitate per se",) as Priestley had done before him, took a most important step in advance of his English predecessor, and beyond his time, and proved that the "mercurial calx" was a compound of "vital air," or the new gas, with mercury, and hence he concluded, by analogy, that all metallic calxes must have a like constitution. Starting thus upon the legitimate, but until then untried path of inductive reasoning in chemistry, he advanced from the fact already made known some years before by the researches of Dr. Black of Edinburgh on "fixed air :" namely that metallic calxes when heated with charcoal were converted into the metallic state with escape of

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