of the bark. Vauquelin later adopted this erroneous theory, and so missed his way. In 1792 Fourcroy got nearer to the truth when he observed incidentally that the water in which the bark had been macerated turned litmus paper green; and he also remarked that lime water caused a greenish precipitate in the infusion. He did not pursue the investigation, but his comment on what he had stated is noteworthy. "These researches," he said, "will no doubt lead to the discovery one day of an anti-periodic febrifuge, which once known may be extracted from various vegetables." Berthollet followed on Fourcroy's lines, but came to the conclusion that the precipitate which lime water gave with decoctions of cinchona was magnesia, which he believed was a constituent of the bark in combination with hydrochloric acid.
In 1811 Gomez, of Lisbon, described a crystalline substance which Dr. Duncan, of Edinburgh, had obtained from certain species of cinchona, and gave to this product the name of cinchonine. Lambert later prepared it in a state of considerable purity. But neither of these chemists suspected its alkaline nature. In 1820 Pelletier and Caventou studied the whole chemistry of cinchona and succeeded in showing that the cinchonine of Gomez was a mixture of two alkaloids, to the second of which they gave the name of quinine. Quinidine was isolated by Henry and Delondre in 1833, and cinchonidine by Winckler in 1844, but the name of the latter was given by Pasteur in 1853. Pasteur also produced the alkaloidal derivatives cinchonicine and quinicine.
Robiquet had the idea that as the coffee plant belongs to the same family of plants as the cinchonas it might be possible to find quinine in coffee. In searching for it he isolated caffeine. This was in 1821. In 1827 Oudry
