the stapes, wall of the labyrinth and posterior half of the mastoid cells. The Eustachian tube may be easily worked out from the tympanic cavity or from the pharyngeal opening. A sagittal section of the middle ear may be made, giving pictures as shown in Figs. 34, 35. The temporal bone is resected as above, the tegmen tympani removed and the bony covering of the Eustachian tube removed with hammer and chisel until the tube is exposed from its pharyngeal opening to the isthmus. The temporal bone is then divided into an outer and an inner half by cutting the roof of the tube with fine straight scissors from the pharyngeal mouth to the bony portion and then cutting the membranous floor of the canal likewise. The bony canal, the floor of the tympanic cavity and the mastoid process are then cut sagittally with a fine fret-saw, passing between the lower annular segment of the sulcus tympani and the inner wall of the tympanic cavity. By altering the direction of the saw-cut the Eustachian tube may be removed in connection with either outer or inner portion of the temporal bone. [Illustration: FIG. 34.—Sagittal section through left middle ear, outer half. an, mastoid antrum; n, niche of the hammer-anvil body; op, mouth of Eustachian tube; te, Eustachian tube; it, isthmus of tube; mt, tympanum; ww, mastoid cells. (After Politzer.) ] [Illustration: FIG. 35.—Sagittal section of left middle ear, inner half. op, mouth of Eustachian tube; te, Eustachian tube; tp, musc. tensor tymp.; p, promontory; st, stapes; sp, musc. staped; f, facial nerve; an, mastoid antrum; ww, mastoid cells; ot, ost. tymp. tubæ; u, lower wall of tympanic cavity. (After Politzer.) ] Other methods of examining the ear are shown in Fig. 32. The tympanic cavity and labyrinth may be removed intact by cutting with a chisel having a cutting edge 3 cm. broad, in the lines _1_, _2_, _3_, _4_, _5_, as shown in Fig. 32. The cut _1_ is made with the chisel held nearly horizontal and parallel with the base of the skull. Cuts _2_, _3_, _4_ and _5_ are made vertically. Great care must be taken not to splinter the bone. A small chisel can be used to connect the ends of the cuts. Soft parts are cut away with the chisel. An elevator is then introduced into cuts _1_ and _2_ and the part lifted out by cutting the remaining soft parts and the articulation of the lower jaw. The portion removed contains the inner section of the external auditory canal, tympanic cavity, ear-drum, a portion of the mastoid cells, the entire labyrinth, auditory and facial nerves.