DISSECTION OF THE HEAD AND NECK 



387 



(dba) Sulcus of promontory (sulcus promontorii). 



(dbb) Subiculum ("support") of promontory (subiculum 



promontorii). 



(dc) Sinus of tympanum (sinus tympani). 



(dd) Fenestra ("window") of cochlea (fenestra cochleae] (0. T. 



fenestra rotunda). 



(dda) Fossula of fenestra of cochlea (fossula fenestrae 



cochleae). 



(ddb) Crest of fenestra of cochlea (crista fenestrae coch- 



leae). 



(de) Cochleariform process (processus cochleariformis). 

 Observe the mastoid cells (cellulae mastoideae) and the tympanic 



cells (cellulae tympanicae}. 

 (e) Membranous wall (paries membranaceus) (0. T. outer wall). 



This consists largely of the membrane of the tympanum, which 

 should now be studied. 



FIG. 188. 



Margo occipitalis- 

 Sulcus sigmoideus~ 



Cellulae mastoideae 



'Membrane and proc- 

 esses in the re- 

 cessus epitympani- 

 cus and in the an- 

 trum tympanicum 

 Cms longum 

 incudis 



Manubrium mallei 

 Membrana tympani 



Pars tympanica ossis 



temporaUs 

 ** Canalis facialis 



(Fattoppii) 

 ^Processus styloideus 



Processus mastoideus 



The lateral wall, paries membranaceus, of the left tympanic cavity, and the entrance to the mastoid 

 cells. The antrum tympanicum contains branching connective -tissue strands. Seen from the medial 

 side. (After Toldt, Anat. Atlas, Wien, 1903, 3 AufL, p. 927, Fig. 1433.) 



Membrane of the Tympanum (Membrana tympani) (O. T. Drum- 

 head). (Figs. 186, 188, and 191-193.) 

 Examine 



(a) Flaccid part (pars flaccida) (0. T. Shrapnell's membrane). 



(b) Tense part (pars tensa). 



(c) Border of membrane of tympanum (limbus membranae tympani). 



(d) Anterior malleolar fold (plica malleolaris anterior). 



(e) Posterior malleolar fold (plica malleolaris posterior). 



These two folds are sometimes called " Prussak's striae." 

 (/) Malleolar prominence (prominentia malleolaris). 

 (g) Malleolar stria (stria malleolaris). 



(h) Umbo ("prominent part") of tympanic membrane (umbo mem- 

 branae tympani). 

 (i) Cutaneous layer (stratum cutaneum). 



