AMMONI'ACUM, or AMMO'NIAC, a gum resin, used in medicine on account of its stimulant and discutient qualities, is obtained from (krona A., a plant of the natural order umbelltferce, a native of Persia—a perennial, about 7 ft. high, with large doubly pinnate leaves. The leaves are about 2 ft. long. The whole plant is abundantly per vaded by a milky juice. which oozes out upon the slightest puncture, and which hard ens, and becomes A. The A. exudes from punctures made by an insect, which appears in great numbers at the time when the plant has attained perfection. Much of it is sent to India, and it is generally imported. into Britain from Bombay, although sometimes from the Levant. It occurs in commerce either in tears, or in masses formed of them, but mixed with impurities. It is whitish, becoming yellow by exposure to the :Amos phere, is softened by the heat of the hand, and has a peculiar heavy unpleasant. smell.
and a nauseous taste, at first mucilaginous and bitter, afterwards acrid. It is not fusi ble, but burns with white crepitating flame, little smoke, and strong smell.—It was for sonic time erroneously supposed to be the produce of a species of heraclewn, the seeds of which were found inclosed in R—A. similar substance is obtained from ferula tingi tuna, an umbelhiferous plant, growing on light sandy soils in the n. of Africa; and is said also to be obtained from P. orientali.v, a native of Asia Minor and of Greece. Both these plants have branched stems, and very compound leaves, somewhat resembling fennel. It would seen that the A. of the ancients was the gum resin of the ferula, which has a more faint odor and less powerful medicinal properties than that of the dorema.