1056 



ORGAN 8 OF SPECIAL SENSE 



contents of the tympanic cavity, and is continuous anteriorly with the mucosa of the 

 tuba auditiva (Eustachian tube) and posteriorly with that of the tympanic (mastoid) 

 antrum and mastoid cells. It is a thin, transparent, vascular membrane intimately 

 united to the periosteum. As it passes from the walls to the contents of the tympanic 

 cavity, besides covering the ligaments of the malleus and the incus and the tendons 

 of the tensor tympani and stapedius muscles, it forms a number cf special folds and 

 pouches. The anterior maheolar fold is reflected from the tympanic membrane 

 over the anterior process and ligament of the malleus and the adjacent part of the 

 chorda tympani, and the posterior malleolar fold, stretching between the manu- 

 brium and the posterior tympanic wall, surrounds the lateral ligament of the malleus 

 and the posterior part of the chorda tympani. Each of these folds presents inferiorly 

 a concave free border, and between them and the tympanic membrane are two blind 

 pouches, the anterior and posterior malleolar recesses or pouches 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 tympanic membrane and the neck of the malleus. Its floor, which is formed by 

 the lateral process of the malleus, is lower than its outlet and, therefore, it may serve 



FIG. 751. MEDIAL SURFACE OP RIGHT MEMBRANA TYMPANI. (Enlarged.) 



Superior malleolar ligament INCUS 



HEAD OF MALLEUS 



CHORDA TYMPANI 



NERVE 



Tendon of tensor 

 tympani 



MANUBRIUM OF MALLEUS 

 Tensor tympani muscle 



TUBA AUDITIVA 



Posterior ligament of 

 incus 



PUSTERIOR PORTION OF 

 EPITYMPANIC RECESS 



BASE OF STAPES 



LENTICULAR PROCESS 

 OF INCUS 



Posterior portion of 

 membrana tympani 



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 obturator membrane, which 

 stretches between its crura. Other inconstant folds have been described. The mu- 

 cosa of the tympanic cavity, except over the tympanic membrane, promontory, and 

 ossicles, is covered by a columnar ciliated epithelium. 



Vessels and nerves. The arteries of the tympanic cavity are the anterior tympanic from 

 the internal maxillary artery (p. 529, fig. 413), the stylo-mastoid from the posterior auricular 

 artery (p. 526), the superficial petrosal from the middle meningeal artery (p. 529), the inferior 

 tympanic from the ascending pharyngeal (p. 518. fig. 408), and the carotico-tympanic branch 

 from the internal carotid. The veins empty into the superior petrosal sinus and into the pos- 

 terior facial (temporo-maxillary) vein (p. 648). The nerves are the tympanic plexus formed by 

 the tympanic branch of the glosso-pharyngeal (p. 981), and the inferior and superior carotico- 

 tympanic nerves from the internal carotid plexus of the sympathetic (p. 1005). The small super- 

 ficial petrosal nerve takes its origin from the tympanic plexus, and the chorda tympani crosses 

 the tympanic cavity from the dorsal to the ventral wall (p. 977, figs. 704 and 751). 



