THE EAR. 91 



of long standing, and the character of the operation is dependent on the extent to 

 . which the disease has progressed. 



In removal of the ossicles, the tympanic membrane is first separated around its 

 edges. Then the tendon of the tensor tympani muscle is cut, and the incus disarticu- 

 lated from the stapes. The latter is done by cutting with a bent knife across the 

 axis of the stapes and not of the incus (see Fig. 105). The malleus is seized and 

 drawn first down and then out, bringing the membrane with it, and afterwards the 

 incus, which is detached by Ludwig's hook (see Fig. 106), is removed, and, if 

 desired, the stapes. Granulations and pus are removed by the snare, forceps or 

 curette. Care is to be taken to avoid, if possible, scraping away the thin shell of 

 bone on the internal wall that covers the facial nerve. Any twitching of the 

 muscles of the face indicates that the nerve is being irritated. The chorda 

 tympani nerve, which passes on the inner side of the handle of the malleus and lies 

 beneath the mucous membrane, is of necessity removed. No important symptoms 

 follow its removal. 



Operations on the Antrum and Mastoid Cells. In order to understand 

 these operations, one must recall that the suprameatal crest is the ridge of bone forming 

 the upper edge of the bony meatus, and a continuation backward of the posterior root 



Suprameatal tri- 

 angle of Macevven 



Suprameatal spine 



Posterior root of zygoma 



FIG. 107. Landmarks for operating to enter the mastoid antrum. 



of the zygoma. The upper and posterior edge of the meatus is formed by a thin, small 

 shell or edge of bone running from the suprameatal crest downward and backward 

 to the posterior wall; this is the suprameatal spine. Behind the suprameatal spine 

 and between it and the posterior portion of the suprameatal crest is a depression, 

 the suprameatal fossa. This suprameatal fossa is triangular in shape. The crest 

 forms the upper side, the spine its anterior side, and the ridge of bone, running from 

 the posterior portion of the crest to the lower portion of the spine, forms the posterior 

 side. These three lines form the suprameatal triangle of Macewen. It is through 

 this triangle tha,t the antrum may be reached. The operation may be restricted to the 

 antrum, and tympanic cavity, or may include the whole or part of the mastoid cells, 

 constituting the operation known as tympanomastoid exenteration. 



To reach the antrum a semicircular cut is made a centimetre back of the ear 

 and the ear and membranous canal loosened and pushed forward. With a gouge 

 chips of bone are removed from the suprameatal spine backward and from the crest 

 downward as far as desired. This will extend considerably beyond the line marking 

 the posterior boundary of Macewen' s triangle. The outer table of bone being 

 removed, the cells are broken through parallel to the meatus and slightly upward, 



