TYMPANUM

(Lat. adrwTw.) The drum of the ear; the cavity behind the membrane of the tympanum, surrounded by the petrous portion of the temporal bone, and terminating at the cochlea of the labyrinth; it contains the four small auditory bones, and the Eustachian tube opens into it. Tympanum, in Architecture, the space in a pediment enclosed by the cornice of the inclined sides and the horizontal fillet of the corona. Tympanum, in Botany, is a membrane stretched acro the mouth of the threa of a mo . [s. 1284]