THE EAR, HEARING, TASTE AND SMELL 227 



has. When a note is sounded in the air near such a membrane, the 

 alternating waves of aerial condensation and rarefaction will move 

 it; and if the waves succeed at the vibratioiial rate of the membrane 

 the latter will be set in powerful sympathetic vibration; if they do 

 not push the membrane at the proper times, their effects will 

 neutralize one another: hence such membranes respond well to 

 only one note. The tympanic membrane, however, responds 

 equally well to a large number of notes; at the least for those due 

 to aerial vibrations of rates from 60 to 4,000 per second, running 

 over eight octaves and constituting those commonly used in 

 music. This faculty depends on two things: (1) the membrane is 

 comparatively loosely and not uniformly stretched; (2) it is loaded 

 by the tympanic bones. 



The drum-membrane is a shallow funnel with its sides convex 

 towards the external auditory meatus; something like an umbrella 

 turned inside out; in such a membrane the tension is not uniform 

 but increases towards the center, and it has accordingly no proper 

 note of its own. Further, whatever tendency such a membrane 

 may have to vibrate rather at one rate than another, is almost com- 

 pletely removed by " damping" it, i. e., placing in contact with it 

 something comparatively heavy and which has to be moved when 

 the membrane vibrates. This is effected by the tympanic bones, 

 fixed to the drum-membrane by the handle of the malleus. An- 

 other advantage is gained by the damping; once a stretched mem- 

 brane is set vibrating it continues so doing for some time; but if 

 loaded its movements cease almost as soon as the moving impulses. 

 The dampers of a piano are for this purpose; and violin-players 

 have to "damp" with the fingers the strings they have used when 

 they wish the note to cease. The tympanic bones act as dampers. 



The Middle Ear (P, Fig. 69) is an irregular cavity in the tem- 

 poral bone, closed externally by the drum membrane. From its 

 inner side the Eustachian tube (R) proceeds to the pharynx, and 

 the mucous membrane of that cavity is continued up the tube to 

 line the middle ear; the proper tympanic membrane composed 

 of connective tissue is therefore covered by mucous membrane on 

 its inner, as it is by very thin skin on its outer, side. In the bony 

 inner wall of the middle ear are two small apertures, the oval and 

 round foramens, o and r, which lead into the labyrinth. During 

 life the round aperture is closed by the lining mucous membrane, 



