prism

A solid the sides of which are parallelograms and its cro section a figure of three or more sides, abducting p's. P's to be held before the eyes with their bases directed toward the nose, so as to cause divergence of the eyes. adducting p's. P's to be held before the eyes with the bases outward, so as to adduct or converge the eyes in ophthalmological examinations, enamel p's. See enamel fibers, under fiber. The solid hexagonal p's, about 0.015 millimeter in diameter, which, standing side by side, form the enamel of the teeth. Nicol's p. A p. made by cutting a crystal of Iceland spar diagonally and cementing the pieces with Canada balsam; used to effect the polarization of light. sarcous p. See sarcous elements, under sarcous. [Gr., prism a, from prize in, to saw.]