LECTURE ir. (J7 



to this opinion, can, I think, only oppose 

 it on the following grounds. They must 

 contend either that the muscles have a kind 

 of perception of injury which causes them 

 to contract, even though they are uncon- 

 nected with the brain ; or that the nerves 

 are the organs which prepare and supply 

 the muscles with something which is the 

 cause of irritability. 



Concerning the first of these suppositions, 

 that muscles may have a perceptibility of 

 injury, distinct from that which we under- 

 stand to be feeling, 1 have to observe, that 

 we can have no idea of sensation but what 

 results from our own experience, which 

 may be defined to be perception attended 

 with consciousness ; which kind of sensa- 

 tion is confined to the brain alone. Of any 

 other kind of perception, it is evident we 

 can never form any idea. 



If a man's leg be amputated, and by 

 voltaic electricity I excite contraction in 

 its muscles for some hours, how can I 

 know whether they feel or not ? We na- 



F 2 



