Ammoniac is a concrete, gummy - resinous juice, usually brought from the East Indies in large masses composed of lumps or tears of a milky colour, but on exposure to the air, it quickly acquires a yellowish appearance. Hitherto we have no certain account of the plant which afifords this juice, but it has, and with some probability, been asserted, that it is a species of the ferula, from another species of which is also produced the asa foetida ;—it is said to grow in Nubia, Abyssinia, and the interior parts of Egypt.

This gum has a nauseous sweetish taste, succeeded by a sensation of bitter; and a smell somewhat resembling, but more grateful than, galbanum. When chewed, it tens in the mouth, and becomes of a white colour. It may be partially dissolved, in water, or in vinegar, with which it assumes the appearance of milk, but the resinous part, amounting to about one half, subsides when suffered to rest. A • similar composition, but much inferior in virtue, is frequently sold under the name of strained gum ammoniac. Those tears which are large, dry, and free from little stones, or other impurities, should be selected and prepared for internal use; the coarser kind may be purified by solution and straining, but unless this be c managed, it will lose a considerable portion of its fine and more volatile parts.

In medicine, it is prescribed for removing obstructions of the abdominal viscera; in hysterical complaints occasioned by the deficiency of periodical evacuations, and in long and obstinate colics, proceeding from viscid matter lodged in the intestines. . A solution of it, in vinegar of squills, has proved of

Considerable service in the humid chronic asthma of the aged and the most convenient form for its exhibition, is that of pills; a scruple may D every night, or oftener. Externally it is used for softening and ripening in-Dt tumours; and with a mixture of squill vinegar, forms a plaister which has sometimes been sue-fully recommended for white swellings. A solution of it, in penny-royal water, is usually kept, in the shoos, under the name of ammoniac milk.