368 



ELEMENTARY PHYSIOLOGY 



LBSS. 



external meatus is surrounded by the concha or external 

 ear {Co. Fig. 118), a broad, peculiarl3'-sliai)ed, and for 

 the most part cartilaginous plate, the general plane of 

 which is at right angles with that of the axis of the 

 auditory opening. The concha can be moved by most 

 animals and by some human beings in various directions 



Co. 



i:.M. 



Fio. lis.— Transverse Section throuoh the Sidr Walls of thb 

 Skull to show the Parts of Ear. 



Co. Concha or external ear; E.M, external auditory meatus; Ty.M, 

 tympanic membrane; Inc. Mall, incus and malleus; A.S.C, P.S.C, 

 E.S.C, anterior, posterior, and external somicircular canals ; Cnc. cochlea ; 

 Eu. Eustachian tube; !.M, internal auditory meatus, through which the 

 auditory nerve passes to the organ of hearing. 



by means of mu.scles, which pass to it from the side of the 

 head. 



(ii) The Middle Ear. — The outer wall of the internal 

 ear is still far away from the exterior of the skull. 

 Between it and the visible opening of the ear, in fact, are 

 placed in a straight line, first, the drum of the ear, or 



