1506 



HUMAN ANATOMY. 



FIG. 1263. 



TroltscrTtfold 



Rout 

 windo 



l'f!iM.iitnr\ 



Posterior 



pensory ligament 

 nt>rana 

 ids 



nterior 

 us pensory 

 ment 



irt process 

 of malleus 

 Anterior fold 



lower portion, the umbo being slightly below the middle of the membrane. By the 

 two lines the membrane is divided into unequal quadrants. This arrangement into 

 quadrants is a very important one since the pathological appearances occurring in 

 each differ greatly. 



The antero-suflerior quadrant corresponds to the tympanic opening of the tube, the 

 canal for the tensor tympani muscle, and the anterior pouch of the drum-head. The 

 antero-inferior quadrant corresponds to the carotid canal. The postcro-superior quad- 

 rant contains the long process of the incus, the stapes, and the articulations of these 

 bones, the oval window, the pyramid, and stapedius muscle, the posterior pouch of 

 the drum-head, the chorda tympani, and the posterior fold (pathologic). 1\\zpostcro- 

 inferior quadrant contains the round window, the tympanic cells in the floor of the 

 tympanic cavity and the bulb of the jugular vein. The flaccid portion or Shrapnell's 

 membrane corresponds to the neck of the malleus and Prussak' s space (Briihl-Politzer). 

 The bulb of the jugular vein may be larger than usual in which case it may 

 encroach upon the posterior half of the membrane. Moreover, it may have an 

 imperfect bony covering when it will be in danger during paracentesis tympani, 

 the place of election of which is in this portion of the membrane. For the same 

 reason, pus in the middle ear may more readily encroach upon the vein. The 



posterior inferior quadrant is 

 selected for openings to evac- 

 uate effusions in the tympanum, 

 because it is less sensitive and 

 vascular than the rest of the 

 membrane and corresponds to 

 less important structures. The 

 opening also gives better drain- 

 age than through any other 

 portion. It should be borne 

 in mind that the floor of the 

 tympanum is 2-3 mm. below 

 the inferior margin of the drum 

 head, so that in the upright 

 position perfect drainage can- 

 not be obtained. The tym- 

 panic membrane has an internal 

 mucous lining, an external 

 cutaneous and an intervening 

 fibrous layer. It, therefore, has 

 little elasticity, so that, while 

 small openings often heal rap- 

 idly, large openings close slowly, or not at all. A permanent opening, however, 

 does not of necessity produce deafness. 



With an aural speculum and good light, one may locate the various structures 

 as follows : Above and in front is seen the short process of the malleus as an appar- 

 ently prominent point. From this point two streaks pass to the periphery, showing 

 the division between the tense portion of the membrane and its flaccid portion 

 (Shrapnell's membrane), seen only in a roomy meatus. Extending backward and 

 downward from this point is seen a whitish streak ending at the umbo. This is the 

 long process or handle of the malleus. Directed downward and forward from the 

 iimbo is an area of liidit with its apex at the umbo and its base near the periphery of 

 the membrane. It is triangular in shape and is due to the funnel shape of the 

 membrane and the resulting light-reflex. Above and in front of the short process of 

 the malleus is the membrane of Shrapnell. Through the grayish translucent tym- 

 panic membrane the contents of the tympanum may sometimes be seen, changing 

 apparently the color of the membrane. Its conical shape has been proven by trial 

 and mathematically to be the most favorable for the reception of sound waves. ' The 

 vibrations are transmitted through the ossicles to the labyrinth by way of the oval 

 uindow. Tin- malleus rests in the membrane, the stapes occupies the oval window 

 and the incus lies between and articulates with the two. 



Light reflex 



Normal drum-head of right side as seen with mirror. X 6. 



