284 I'ilYMOLiMiY OF MTSCLES AND NKItVKS. 



end of the nerve of hearing, then the sound of an 

 orchestra would elicit in us the sensation of light and 

 colour, ami the sight of a highly coloured picture 

 \v. mid elicit in us impressions of sound. The sensa- 

 tions which we receive from outward impressions arc 

 therefore not dependent on the nature of these im- 

 pres.-ions, but on the nature of our nerve-cells. We 

 feel not that which acts on our bodies, but only that 

 which goes on in our brain. 



Under these circumstances it may appear strange 

 that our sensations and the outward processes by 

 which they are evoked are so entirely in agreement ; 

 that light elicits seii.-ati<>ns of 'light, sound sensations 

 of sound, and so on. But this agreement does not really 

 exist ; its apparent existence is only due to the use of 

 the same name to express two processes which have 

 nothing in common. The process of the sensation of 

 light bears no likeness to the physical process of the 

 ether vibrations which elicit it; and this is evident 

 even iii the fact that the same vibrations of ether 

 meet ing the skin elicit an entirely different sensation, 

 namely, that of warmth. The vibrations of a tuning-fork 

 are capable of exciting the nerves of the human skin, 



and then they are felt ; they may excite our auditory 

 n. r\.--. and then they are heard: and under certain 

 eirctim-lances they may lie seen. The vibrations of 

 the tuning-fork are always the same, and they have 

 nothing in common with tin- sensations which th<\ 

 elicit. Though the phy>ical processes of the \iliration- 

 of ether are called. ~, unet inies li^ht. and at another time 

 heat, a more accurate study of phy-ic- sho\\< that the 



is the same. The usual classification of physical 



into t ho-e of sound, 1 igli t , warmth, and so on. 



