526 STUDIES IN ADVANCED PHYSIOLOGY. 



cells up and down or this friction of their delicate hairs in 

 the reticular membrane, or possibly both of these which 

 serve as a stimulus for the nervous impulse, is beyond 

 question. 



Here is the point at which the physical vibrations give 

 rise to physiological, that is, nervous impulses, but it must 

 be borne in mind after all that the real conscious apprecia- 

 tion of sound occurs only in the auditory centers in the 

 brain. Sound is a purely psychological experience, and the 

 ear and the nerves leading from it to the brain serve merely 

 as accessory pieces of apparatus to call into being these 

 psychical acts. 



Very few sounds, however, are so simple as to affect but 

 a single string of the basilar membrane. Most sounds are 

 composite sounds (hence their quality) and frequently 

 composite sounds in turn are blended into harmonies. The 

 ear, however, has the ability to perceive all the individual 

 sounds that enter into such a composition and so we must 

 imagine that in the perception of the concert note there are 

 as many strings of the basilar membrane thrown into vibra- 

 tion as there are individual component notes in the concert.- 

 The ear is even able to analyze such a concert note so care- 

 fully that it may follow some of the individual notes in it. 

 No one finds it difficult when hearing the rendition of an 

 orchestral piece of music to follow a certain instrument, or 

 in a chorus to listen with special attention to a certain 

 voice. This analysis is possible because in the basilar 

 membrane as many individual strings are affected as there 

 are such component notes. 



A somewhat interesting question arises when we remem- 

 ber that although the ear has only about 3,000 strings it is 

 able to perceive many more than 3,000 pitches. This may 

 seem at first inexplicable. Possibly the explanation may 

 consist in assuming that when a pitch is sounded which 

 has not its direct counterpart in the ear but lies between 

 the pitches of two adjoining strings, it will affect both of 

 them, and this possible blending may give rise to a new 



