The =attic= contains the head of the malleus and the body and short process of the incus, and communicates posteriorly with the antrum by a variable sized opening--the aditus. Its roof, the tegmen tympani, a plate of bone frequently of extreme thinness, separates the cavity of the middle ear from the middle fossa of the cranium. The facial canal extends backwards along the inner and upper border of the tympanic cavity, passing above the vestibule and the fenestra ovalis to curve downwards posteriorly beneath the external semicircular canal, which at this point forms the inner and inferior boundary of the aditus. The =ossicles= form a movable chain fixed at three points: namely, the attachment of the handle of the malleus to the tympanic membrane; the posterior ligament of the incus, a feeble structure, binding its short process to the entrance of the antrum; and the strong annular ligament connecting the footplate of the stapes to the margins of the fenestra ovalis. In addition, the anterior, external, and superior ligaments of the malleus also tend to keep it in position and limit its movements. [Illustration: FIG. 186. ANATOMICAL PREPARATION OF THE MIDDLE EAR. 1-1/2 nat. size. 1, Antrum; 2, Aditus; 3, Attic, containing head of malleus and body of incus; 4, Chorda tympani nerve; 5, Middle fossa of intracranial cavity; 6, Eustachian tube; 7, Carotid canal; 8, Jugular vein in jugular fossa; 9, ‘Cellar’ or floor of tympanic cavity; 10, Canal of facial nerve; 11, Sigmoid groove for lateral sinus. (From the Author’s _Diseases of the Ear_.)] The tensor tympani muscle, extending from the processus cochleariformis, crosses the tympanic cavity to be inserted into the inner margin of the neck of the malleus; and the stapedius muscle emerging from the apex of the eminentia pyramidalis is inserted into the head of the stapes. These ligaments and muscles partially divide the cavity into smaller compartments, such as the outer attic and Prussak’s space, so that in some cases inflammation may be limited to only a part of the tympanic cavity; a fact to be remembered in considering the question of operative procedures. OPERATIONS UPON THE TYMPANIC MEMBRANE PARACENTESIS =Indications.= The chief object of paracentesis (myringotomy or simple incision) is to permit of escape of fluid from the tympanic cavity. (i) _In acute inflammation of the middle ear_, if the acute symptoms continue in spite of palliative treatment, and the following conditions are present:--(_a_) An increasing congestion and bulging of the tympanic membrane, especially if accompanied by earache and pyrexia. (_b_) The obvious presence of pus within the tympanic cavity, shown by a circumscribed, angry red or yellow protuberance on the tympanic membrane. (_c_) Accompanying cerebral symptoms, such as drowsiness, vomiting, vertigo, and convulsions. (_d_) Tenderness over the mastoid process. (_e_) Paroxysms of pain acute enough to prevent sleep.