re oi ih 
‘os aie 
squamous suture. The floor (fundus tympani seu paries jugularis) is narrower than 
the roof and consists of a thin plate of bone, which separates the cavity from the 
fossa jugularis; anteriorly, it extends upwards and becomes continuous with the 
Antrum mastoideum 
Recessus epitympanicus | cS 
MIDDLE EAR OR TYMPANIC CAVITY. 705 
Fenestra ovalis 
Canal for tensor tympani— Pyramid 
We gr” » 
Processus cochleariformis za Za 
7 , 
; —— Sinus tympani 
Promontory with ya 
grooves for 
tympanic plexus” 
Osseous part of 
Eustachian tube~ 
Bristle introduced into the 
foramen for Jacobson’s nerve 
Mastoid air-cells 
Fossula rotunda 
A, ‘ 
sw 
’ [rial 
Course of canalis facialis 
Fic. 515.—SEcTION THROUGH LEFT TEMPORAL BONE, showing inner wall of tympanic cavity, etc. 
posterior wall of the carotid canal. The inner orifice for Jacobson’s nerve, or 
tympanic branch of the glosso-pharyngeal, is seen near the junction of the floor with 
the inner wall. 
The posterior wall (paries mastoidea) presents, from above downwards: (1) A 
rounded or triangular opening, which extends backwards from the recessus epitym- 
panicus and leads into the mastoid antrum (Fig. 515). The mastoid antrum will be 
again referred to (p. 708). (2) A depression, the fossa incudis (Fig. 516), for the 
lodgment of theshort Recessns epitympanicus 
process of the incus; iy) 
this fossa is situated = a — Z 
in the postero-infer- ° 
ior part of the reces- 
sus epitympanicus. 
(3) A minute coni- 
cal bony projection, — ,,.¢ 
the pyramid or emi- Apertura 
nentia pyramidalis ‘pines 
(igh 515)pthesum-= chords 
mit of which is per- 
forated by a round 
aperture for the pas- 
sage of the tendon 
of the stapedius 
muscle. This aper- 
ture is continued 
downwards and Fic. 516.—Lert MEMBRANA TYMPANI AND RECESSUS EPITYMPANICUS, viewed 
backwards as a canal from within. The head and neck of the malleus have been removed to 
Pepnkeor the Fal , show the membrana flaccida and the tympano-malleolar folds. x 3. 
al- 
lopian aqueduct, and opens, by a minute orifice, on the base of the skull in front of the 
stylo-mastoid foramen. It communicates with the Fallopian aqueduct by one or two 
small foramina, through which the vessels and nerve pass to reach the stapedius 
muscle. A minute spicule of bone often extends from the pyramid to the promontory 
on the inner wall of the tympanum. (4) A small aperture, the apertura tympanica 
canaliculi chorde (Fig. 516); this is situated immediately internal to the posterior 
edge of the membrana tympani, nearly on a level with the upper end of the manu- 
brium mallei. (5) A rounded eminence, the prominentia styloidea, is sometimes 
| 45 
Membrana flaccida 
(Shrapnell) 
Anterior and posterior 
tympano-malleolar folds 
—Tendon of tensor 
tympani muscle (cut) 
Manubrium mallei 
i) 
7 Membrana tensa 
i. 
Qe 
Sulcus tympanicus 
