CHAPTER III 



GENESIS OF THE NERVOUS SYSTEM 



TYNDALL says : " I have here a bell-formed glass 

 bowl placed mouth upwards and supported on its 

 base. I pass a violin bow across the edge, and I 

 hear a sound. If I pour sand into the bowl, it 

 takes the form of a regular figure ; and if I fill 

 the bowl with water, its surface is ruffled by 

 beautiful undulations. These waves show that the 

 bowl, on emitting a sound, divides into four 

 vibrating portions, separated from one another by 

 non-vibrating lines." It is well known by analysis 

 that the different colours which appear in white light 

 are due to differences in the number of vibrations ; 

 that is to say, the colours are distinguished from 

 each other for the same reason as one sound is dis- 

 tinguished from another in an instrument of music. 

 It is now known that sound, heat, light, 

 electricity, and radio-activity are different from 

 each other because they are diverse modes of 

 vibrations or movements. 



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