416 THE BODY AT WORK 



responds to tones of different pitch, or analyses compound 

 tones, is not as yet even approximately solved. To escape the 

 acoustic difficulties which have to be faced by anyone who 

 endeavours to expound the theory of the cochlea as a piece of 

 analytical apparatus, various suggestions as to the possibility 

 of an action en masse have been advanced. For example, the 

 basilar membrane has been compared to a telephone-plate 

 which takes up vibrations and transmits them through the 

 auditory nerve to the brain. But if the organ of Corti be the 

 transmitter, there is no ear in the brain to analyse the vibra- 

 tions given out by a receiving telephone-plate ; and without a 

 receiving plate and a listening ear a telephone is purposeless. 

 According to this hypothesis, the basilar membrane vibrates as 

 a whole, moving the hair-cells in various " patterns "; the pres- 

 sure of the hairs against the tectorial membrane causing irrita- 

 tion of, the cells which bear them, and hence producing stimula- 

 tion of various groups of nerves. Other pattern theories are 

 somewhat similar. But it is obvious that all hypotheses of the 

 vibration of the whole of the basilar membrane, or of large 

 parts of it, simultaneously, leave to the mind the responsibility 

 of reading the pattern which the impulses generated in the 

 organ of Corti make in the brain. It is conceivable that every 

 fraction of a semitone which a musician can discriminate, and 

 every combination of tones which he can analyse, is trans- 

 mitted to the brain by a large number of co-operating nerve- 

 impulses ; but such a theory involves a complexity of mental 

 associations difficult to contemplate. 



According to the general principles enunciated in this book, 

 analysis of stimuli is the function of sense-organs. It cannot 

 in all cases be compared with the analysis effected in a physical 

 laboratory ; nor is this necessary ; but it must be carried so far 

 that nerve-impulses which have no specific qualities apart from 

 their source shall give rise to effects in consciousness which 

 have no basis other than the topographical distribution of the 

 said impulses in the brain. There may be sensory impulses 

 of different orders ; there may be in the brain psycho- 

 physical substances which react to impulses of various orders 

 in various ways ; but until we have some hint of the 

 existence of specific impulses and specific psycho-physical 

 substances, we are not justified in postulating their existence 



