1090 



SPECIAL SENSE ORGANS 



of Troltsch. Connected with the posterior recess is a third cul-de-sac, the superior recess of 

 the tympanic membrane, or pouch of Prussak, situated between the pars flaccida of the tym- 

 panic membrane and the neck of the malleus. The floor of this recess is formed by the lateral 

 process of the malleus, and is lower than its outlet; therefore, the recess may serve as a pocket- 

 in which pus or other fluid may accumulate. A somewhat variable fold of mucosa, the plica 

 incudis, passes from the roof of the tympanic cavity to the body and short process of the incus. 

 The body and short process of the incus, the head of the malleus, and this fold incompletely 

 separate off a lateral cupular portion of the epitympanic recess, and a stapedial fold stretches 

 from the posterior wall of the tympanic cavity and surrounds the stapes, including the oburator 

 membrane, which stretches between its crura. Other inconstant folds have been described. 

 The mucosa of the typanic cavity, except over the tj^mpanic membrane, promontory, and 

 ossicles, is covered by a columnar ciliated epithelium. 



Fig. 834. — The Tympanic Cavity, Anterior Wall Removed. 



Epitympanic recess 



Lateral malleolar 



ligament 



Pars flaccida 



Superior recess 



Lateral process of 



malleus 

 Anterior malleolar 



ligament 



Insertion of tensor 



tampani 



Manubrium of 

 malleus 

 External acoustic 

 meatus 



Umbo and tip of 

 manubrium of 

 malleus 



Limbus 

 Annulus 



Tympanic cellulae 



Superior malleolai 

 ligament 



Incus 



Head of malleus 



Neck of malleus 



Facial nerve 

 Long process of 



incus 

 ■Pyramidal 



eminence 

 ^Tendon of 

 stapedius 



Bones. — The tympanic cavity contains three small movable bones, joined to- 

 gether and to the walls of the cavity, and having attached to them special muscles 

 and ligaments. These auditory ossicles form a chain across the tympanic cavity 

 connecting the tympanic membrane and the vestibular (oval) fenestra. They are 

 the malleus, the incus, and the stapes, and are described in the section on Oste- 

 ology on p. 79. 



Articulations of the ossicles. — The manubrium and lateral process of the malleus are im- 

 oedded in the tympanic membrane. The margin of the irregularly elliptical articular surface 

 bn the posterior side of the head of the malleus is bound to the body of the incus by a thin 

 capsular ligament, forming a diarthrodial joint, the incudo-malleolar articulation. From the 

 inner surface of the capsular ligament, a wedge-shaped rim projects into the joint cavity and 

 incompletely divides it. The long crus of the incus lies parallel to the manubrium of the 

 malleus and on its superior and medial aspect (figs. 833 and 835). It ends in the lenticular 

 process. The convex extremity of this fits into the concavity on the head of the stapes, to 

 form a diarth/odial joint, the incudo-stapedial articulation. From its articulation with the 

 incus, the stupes pusses almost horizontally acrciss the tympanic cavity to its junction with 

 the medial wall. Tlio cartilage-covered edge of the baye is bound to the cartilage-covered rim 

 of the vcstil)ular Coval) fenestra by the annular ligament of the base of the stapes, thus forming 

 the tympano-stapedial syndesmosis. 



Ligaments of the ossicles. — In addition to the attachment of the manubrium 

 of the malleu.s and the base of the stapes to the walls of tiie tympanic cavity, the 

 bones have additional ligamentous attachments. The superior malleolar liga- 



