This gum-resin will be hereafter treated of as a stimulant expectorant, when its origin, properties, composition, and physiological effects will be detailed. In the present place it is sufficient to state that, along with other properties, it is supposed to possess those of a nervous stimulant, in a degree somewhat less than the two preceding gum-resins. In this capacity, it has been considered useful in obstinate colicky affections of the bowels with constipation, and in asthma complicated with chronic bronchitis, being aided in the former of these affections by its laxative, and in the latter by its expectorant properties. The dose of it is from ten to thirty grains, given in the form of pill or emulsion.

Ammoniac is used externally, as a local stimulant, in the form of Plaster (Emplastrum Ammoniaci, U. S.). This often produces a papulous eruption, and sometimes considerable inflammation of the skin. It is used chiefly to promote resolution of scrofulous tumours, and other chronic swellings of the joints. Combined with mercury, as it is in the Plaster of Ammoniac with Mercury (Emplastrum Ammoniaci cum Hydrargyro, U. S., Br.), it acquires increased discutient powers; and in this form is applied additionally to venereal nodes and tumefactions, and over the region of the liver in chronic hepatitis. This plaster sometimes affects the gums.