Active Ingredients. - The principal ingredients of pyrethrum are three in number; (1) an acrid fixed resin, pyrethrine, insoluble in caustic potash; (2) a second resin; (3) an acrid yellow oil, both of which latter are soluble in the alkali mentioned. The root contains likewise inuline, tannin, and various unimportant substances.

Physiological Action. - The root of this plant, when dry, is scentless. On chewing it, there is soon perceived on the lips and tongue a peculiar pricking sensation, accompanied by heat. Acridity and pungency are then detected, and an abundant flow of saliva and of buccal mucus soon ensues. "The heat," says Grew, "is joined with a kind of vibration, as when a flame is brandished: this heat is by no means painful." When applied to the skin, the root acts as a rubefacient; and in all cases the effects appear to be due to the pyrethrine.

Therapeutic Action. - The chief employment of this drug is as a masticatory and sialagogue; it is recommended also in rheumatic and neuralgic affections of the head and face, and in cases of palsy of the tongue. When resorted to for any of these purposes, the patient should chew the root.

Pyrethrum is again very useful as a stimulant, in the form of gargle or lotion, when there is partial or entire obstruction of the sublingual or sub-maxillary glands. The gargle prepared from it was formerly prescribed also for relaxed uvula, and for partial paralysis of the tongue and lips. The tincture is useful for toothache.

Preparations And Dose. - Tinctura Pyrethri (B. Ph.). Not used internally; - when required for toothache - a few drops should be applied on cotton-wool. When used as a gargle, two or three drachms of the tincture in a pint of water.