92 University of California Puhlications in Anatomy [Vol. 



Chapter XII 



AN ATTEMPT TO EXPLAIN THE MINUTE FUNCTION OP 

 THE AUDITORY SYSTEM 



The first successful attempt to explain the nature of the subjective 

 processes in audition with the help of structures of the inner ear was 

 made sometime ago in the classic work of Ilelmholtz (1^63). In his 

 theory of hearing he postulated structures in the inner ear which 

 would act as analyzers of the complex physical acoustic phenomena as 

 they usually exist in the surrounding world. (Most sounds are phj'sic- 

 ally "complex" only in the sense that they can be decomposed by 

 special procedures into simple sinusoid vibrations ; without such an 

 artificial decomposition they form undivided, though not simple 

 sinusoid vibrations; Hornbostel, 1926.) Sound analyzers of the 

 cochlea have been identified with various non-nervous structures sup- 

 porting sensitive hair cells of the papilla acustica basilaris. Most 

 probably they are the elastic chords or strings composing the basilar 

 membrane of the cochlea. (See Held, 1926.) By these the seemingly 

 complex physical acoustic phenomena would be decomposed into their 

 elementary or primitive constituents, into single, independent, simple 

 sinusoid vibrations, corresponding with simple tones. These latter 

 would by resonance cause a co-vibration of special groups of cochlear 

 analyzers or strings, always the same for the same tone, and would 

 thus stimulate certain, definite hair cells mounted upon the basilar 

 membrane in the papilla acustica basilaris or the organ of Corti. In 

 addition it can be said that Helmholtz' resonance theory of hearing 

 implies an independent and separate transmission centralward, to the 

 cerebral cortex, of definite independent stimulations intercepted by 

 separate groups of hair cells. Each nervous current initiated by the 

 stimulation of a given group of cochlear hair cells by using its own 

 portion of the central auditory path would reach the auditory pro- 

 jection cortex without being deprived of its original, primitive form. 

 It would be the task of the cortex itself to put together once more 

 the elementary auditory neuro-biological phenomena into more com- 

 plex cortical forms. Prom this angle, the function of the cochlear 

 apparatus appears exclusively as one of analyzing or decomposing, 

 the synthetic or integrative process in the audition being imagined as 

 performed exclusively by the cortex. 



