i'ris. 1

A thin, circular, contractile membrane, hanging vertically like a curtain in the anterior chamber of the eye. Its posterior surface is covered with pigment. It contains a set of circular muscular fibers, the sphincter, which contracts the pupil; and radiating fibers of elastic ti ue which dilate the pupil. 2. A genus of iridaceous herbs. 3. Of the U. S. Ph., blue flag, the rhizome and rootlets of /. versicolor. I. flor ent in a. In the U. S. Secondary List, 1870, orris root, obtained from /. germanic a, I. pallid a,, and I. flor ent in a, cathartic, and in large doses emetic; once used as a diuretic in dropsy, but now chiefly employed, on account of its delicate violet odor, as an ingredient in tooth powders and perfumes. I. verna, I. vernata. Vernal i.; a species growing in the southern United States. The root is purgative. I. versicolor. The larger blue flag of North America, the root of which has cathartic, emetic, and diuretic properties. [Gr., iris, a rainbow.]