318 THE SENSES 



tion, 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 nbro-cartilaginous process 

 projecting backward in front of the concha, the tragus. The 



FIG. 90. Scheme of the organ of hearing. 



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

 (h) , short process (kf) and handle (m) ; a, incus, its short process (x) and its long 

 process united to the stapes (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 runs inward and slightly forward from 

 the concha to terminate at the membrana tympani, or drum. 

 Its inner part is in the petrous portion of the temporal bone; its 

 external part is nbro-cartilaginous in structure. The whole is 

 lined by integument. 



The Middle Ear (Tympanum). This is a cavity at the 

 bottom of the external auditory canal in the petrous portion of 



