196 PHYSIOLOGY CHAP. 



tragus, antitrasrus, lobule, and the concha which surrounds the 



O ' O ' * 



entrance to the meatus. The muscles which move the pinna as a 

 whole are the retractor, adductor, and elevator, while those which 

 alter its form were described by Valsalva aa the tragicus, anti- 

 tragicus, helicis major and minor, transversus and obliquus 

 auriculae. These muscles are well developed in animals, in which 

 the pinna is capable of a number of expressional movements, but 

 in man they are rudimentary and practically disused, few people 

 (of whom Johannes Miiller was one) being able to move their ears 

 at will. So that while, anatomically speaking, the pinna is a 

 typical organ, containing all the parts corresponding to those in 

 other mammals, physiologically it is an organ that is under- 

 going functional retrogression, and has almost entirely lost the 

 significance it possesses in other animals. Recently (1911) Ch. 

 Fernet has proposed to cure certain forms of serni-deafness by 

 means of auricular ////////m.sV/V.s, the aim of which is by appropriate 

 exercises to recover the voluntary functions of the external 

 muscles of the ear. 



In order fully to understand the functions of the pinna it is 

 desirable to study it, in the first place, not in man, but in an 

 animal in which it is highly developed, e.g. the ass, where its 

 function is that of a trumpet, which collects and condenses the 

 sound-waves. If we apply a long trumpet to our ear, we recognise 

 at once that it is a great help in hearing ; the ticking of a watch 

 can be heard at a much greater distance than with the unaided 

 ear. The sound-waves which enter the large aperture of the 

 trumpet with the air are reflected along its walls, so that the 

 waves that reach the meatus are exaggerated. The ears of 

 donkeys and horses, which are mobile, can moreover be turned 

 towards the source of the sound, and thus fulfil the function 

 of hearing-trumpets, whatever the position of the animal. In 

 addition they have dilator and constrictor muscles, so that they 

 can increase or diminish at will the intensity of the sound-waves 

 that reach them. 



The human ear, on the contrary, is ill-adapted to this purpose. 

 Its form is very unlike a trumpet, and it has become immobile 

 from disuse. The small importance of the human pinna in 

 audition is shown in the fact that its removal affects the delicacy 

 of hearing very little. If the inequalities of the pinna are filled 

 up with wax or plastidine, this has practically the same effect 

 as amputation of the lobe. Schneider found that audition was 

 slightly diminished ; Harless and Esser noticed hardly any differ- 

 ence. Experiments made by Gradenigo on an individual with 

 normal hearing who had lost a lobe showed that the perception 

 of weak, high tones, e.g. the ticking of a watch, was facilitated, 

 while loud, deep tones were not perceptibly reinforced. Hence 

 it is clear that a large portion of the sound-waves that reach the 



