THE EXTERNAL EAR 



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the external, the middle and the internal ear ; the last con- 

 tains the essentials of the auditory apparatus, the external 

 and middle divisions serving only to concentrate the sound 

 waves upon the parts of the internal. 

 The External Ear. This consists of the pinna and the 



FIG. 90. Scheme of the organ of hearing. 



AG, external auditory meatus; T, tympanic membrane; K, malleus with its 

 head (/i) short process (kf) and handle (t) ; a, incus, its short process (x) 

 and its long process united to the staples (s) by means of the Sylvian ossicle 

 (Z); P, middle ear; o, fenestra ovalis; r, fenestra rotunda; x, beginning of 

 the lamina spiralis of the cochlea; pt, scala tympani, and vt, scala vestibuli; V , 

 vestibule; S, saccule; U, utricle; H, semicircular canals; TE, Eustachian tube. 

 The long arrow indicates the line of traction of the tensor tympani; the short 

 curved one, that of the stapedius. (Landois.) 



external auditory canal. The pinna is the external visible 

 portion, and consists of the large cavity, the concha, into 

 which the external auditory canal opens externally ; 

 of two prominent ridges partly surrounding the concha, the 

 helix outside and the antehelix internal to this; and of a 

 fibro-cartilaginous process projecting backward in front of 

 the concha, the tragus. The external auditory canal runs 



