208 SPECIAL SENSES. 



In view of all facts and considerations for and against 

 the theory which we have given of the action of the tym- 

 panic membrane in the appreciation of musical sounds, does 

 it not seem probable that there are, acting upon this mem- 

 brane, muscles of auditory accommodation, analogous in 

 their operation to the muscle of visual accommodation ? We 

 have carefully studied this subject in all its bearings, and, if 

 the reader follow closely our process of reasoning, it must 

 seem probable that the muscles of the middle ear are muscles 

 of auditory accommodation ; but it should be remembered 

 that the action of the membrane is not absolutely essential, 

 and that musical tones, however conducted, must of necessity 

 be correctly appreciated, whenever and however they find 

 their way to the auditory nerves. 1 



Experiments, to which we have already referred in an- 

 other volume, 2 have shown pretty conclusively that the tym- 

 panic membrane vibrates more forcibly when, relaxed than 

 when it is tense. It is evident that the relaxed membrane 

 must undergo vibrations of greater amplitude than when it is 

 under strong tensio*n. In certain cases of facial palsy, in 

 which it is probable that the branch of the facial going to 

 the tensor tympani was affected, the ear became painfully 

 sensitive to powerful impressions of sound. This probably 

 has no relation to pitch, and most sounds that are painfully 

 loud are comparatively grave. The tension of the membrane 

 may be modified as a means of protection of the ear, but the 

 facts belonging to cases of facial palsy are all that we have 



1 Bonnafont has proposed a theory of the action of the membrana tympani 

 in audition, in which the membrane is supposed to undergo partial tensions and 

 relaxations, and thus to bring certain portions of it in unison with different tones. 

 It is difficult to see how this could be demonstrated, even should it occur ; and 

 it is easier to expjain the appreciation of harmonious combinations of tones, by 

 the well-known laws regulating the vibrations of membranes by influence. 

 (BONNAFONT, Traite theorique et pratique des maladies de Voreille, Paris, 1873, 

 p. 277.) Bonnafont published a memoir, in which the above-mentioned theory 

 was proposed, in 1859. 



2 See vol. iv., Nervous System, p. 155. 



