it existed. At the same time the fact should here be stated that the terms "oxidation" and "reduction," which came into use during the following century, developed out of this theory of phlogiston.
Friedrich Hoffmann.—Friedrich Hoffmann was born at Halle, Prussian Saxony, February 19, 1660, and received his medical education in his native city, largely under the direction of his father, who was himself a physician. In 1678 he attended lectures at the University of Jena, and in the following year visited Erfurt in order to benefit from the instruction of Caspar Cramer, who was at that time a distinguished authority in chemistry. At the end of two years he returned to Jena, took his degree of Doctor of Medicine, and acquired the right to deliver public lectures. Then, during the following three years, he visited Holland and England, and, upon his return in 1685, settled at Minden, Westphalia, as a general practitioner of medicine. In 1686 he was appointed District Physician of the Principality of Minden and also Court Physician of the Prince Elector; and two years later he accepted the position of District Physician at Halberstadt. After the inauguration of the new university at Halle, July 12, 1694, Hoffmann appears as one of the earliest professors chosen to serve the institution. In 1701, when Frederick the Third, Electoral Prince of Prussia, assumed the crown under the title of Frederick the First, King of Prussia, he extended to Hoffmann an invitation to come to Berlin and accept the position of Private Physician to His Majesty. Hoffmann was not at first willing to accept the invitation, but in 1708, when the King, who had then become seriously ill, renewed his request, Hoffmann accepted, on condition that he might retain his professorship. In 1712 he returned to Halle and remained there until he died in 1742.
Before Hoffmann's time very little was known concerning the nature of carbonous (or carbonic) oxide and concerning the fatal effects which may be produced by inhalation of this gas. It was a common belief, for example, that the gas was given off by freshly plastered walls; and—as an even worse error—the theological authorities showed an incli-
