MEDICINAL PART. The rhizome.
    Description. Blue Flag is an indigenous plant, with a fleshy, fibrous rhizome. The stem is two or three feet in height, round on one side, acute on the other, and frequently branched. The leaves are ensiform, about a foot long, half an inch to an inch wide. The fruit a three-celled capsule.
    History. Blue Flag is common throughout the United States, growing in moist places, and bearing blue or purple flowers from May to July. The root has a peculiar odor, augmented by rubbing or pulverizing, and a disagreeable taste. It imparts its virtues to boiling water, alcohol, or ether. The root should be sliced transversely, dried, and placed in dark vessels, well closed, and placed in a dark place; it will then preserve its virtues for a long time. The oleo-resin obtained from it is called Iridin, its active principle.
    Properties and Uses. -- This is one among our most valuable medicinal plants, capable of extensive use. It is alterative, cathartic, sialogogue, vermifuge, and diuretic. In scrofula and syphilis it acts as a powerful and efficient agent, and I employ it in my special treatment of chronic diseases extensively and successfully. It is useful in chronic hepatic, renal, and splenitic affections, but had best be combined with mandrake, poke, black cohosh, etc. It will sometimes salivate, but it need cause no apprehension; and when this effect is established, it may be distinguished from mercurial salivation by absence of stench, sponginess of the gums, and loosening of the teeth.
    Dose. -- Powdered root, five to ten grains; Iridin, one grain.