CHAPTER XXXIV. 

 THE EAK AND HEARING. 



The External Ear. The auditory organ in man consists 

 of three portions, known respectively as the external ear, the 

 middle ear or tympanum, and the internal ear or labyrinth; 

 the latter contains the end organs of the auditory nerve. 

 The external ear consists of the expansion seen on the ex- 

 terior of the head, called the concha, M, Fig. 162, and a pas- 

 sage leading in from it, the external auditory meatus, 6r. 



FIG. 162. Semidiagrammatic section through the right ear (Czermak). M, 

 concha; (?, external auditory meatus ; T, tympanic membrane ; P, tympanic 

 cavity ; o, oval foramen ; r, round foramen ; R, pharyngeal opening of Eusta- 

 chian tube ; V, vestibule ; B, a semicircular canal ; S, the cochlea ; Vt, scala ves- 

 tibuli ; Pt, scala tympani ; A, auditory nerve. 



This passage is closed at its inner end by the tympanic or 

 drum membrane, T. It is lined by skin, through which 

 numerous small glands, secreting the wax of the ear, open. 



The Tympanum (P, Fig. 162) is an irregular cavity in 

 the temporal bone, closed externally by the drum membrane* 



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