CHAPTER XXXIV. 



THE EAR 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 7&fly- 

 rinth} the latter contains the end organs of the auditory 

 nerve. The external ear consist of the expansion seen on 

 ihe exterior of the head, called the concha, M, Fig. 143, 

 -and a passage leading in from it, the external auditory 



FIG. 143. Semidiagrammatic section through the right ear (Czermak). AY, 

 concha; G, external auditQvmeatxis ; T, tympanic membrane; P, tympanic 

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

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

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



meatus, G. 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. 



