v THE SENSE OF HEAEING 197 



pinna are reflected outwards, and do not sensibly increase the 

 number of those that penetrate the meatus. 



If the pinna were placed at an angle of 40 directed forwards 

 it would certainly fulfil its function as an auditory trumpet much 

 better, although psychiatrists regard the protruding ear as a 

 morphological sign of degeneration, and aesthetic considerations 

 would, in any case, depreciate such an advantage. Those who are 

 hard of hearing, however, instinctively use their hand to bend the 

 lobe forward, and thus make it fulfil the office of a sound-collector. 



It has been said that the cartilage of the ear may serve as an 

 elastic lamina to receive the sound-waves and transmit them 

 through the bones to the internal ear. But if the meatus is 

 stopped with wax and a watch applied to the pinna we can 

 scarcely hear its ticking, while if it is applied to the mastoid 

 process the sound becomes plainly audible ; the cartilages of the 

 lobe are consequently poor conductors of sound. 



Is the pinna of any importance in recognising the direction of 

 sounds ? The appreciation of the direction of sound will be con- 

 sidered later in discussing binaural audition. The pinna un- 

 doubtedly has a certain importance in this connection : when we 

 turn the ear towards the source of a sound, it is under the most 

 favourable conditions for reflecting the wave towards the auditory 

 meatus. When the sound comes from in front, and still more 

 when it comes from behind, the ear is in an unfavourable position. 

 If we use one ear only, while the other is stopped with wax and 

 the eyes blindfolded, we are able to judge correctly of the direction 

 of a sound, by observing how its intensity varies when we move 

 our head in different directions. 



Weber maintained that we could judge the direction of a 

 sound by means of the pinna because the sound-waves excite its 

 tactile organs. But every-day experience teaches that the sound- 

 waves in the air excite our sense of touch only when they are of 

 extreme intensity, even in regions, in which the body is far more 

 sensitive than is the skin of the auricle. 



Buchanan and, at a later time, Kuss and Duval, Beaunis, and 

 Gelle held that the pinna, independent of the movements of the 

 head, reflects towards the meatus the sound-waves that impinge 

 upon its anterior surface, and arrests those which reach its pos- 

 terior surface. There would thus be an area behind the pinnae 

 in which the vibrations would have difficulty in reaching the ear; 

 and this could be utilised to discover whether the source of sound 

 lay before or behind the head. 



To demonstrate this fact Gelle pointed out that if a watch is 

 held horizontally to the ear, first in front, then at the side, then 

 behind the head, and is gradually moved farther away, so as to 

 discover the distance at which the ticking can be appreciated, it 

 is easy to show that this distance is least behind the ear and 



o i 



