CONSCIOUSNESS AND SENSATION. 93 



impression is conducted to the seat of consciousness 

 in the cerebral hemispheres, corpuscles there enter 

 into a corresponding condition to that of the con- 

 ducting nerve, precisely as a corpuscle which is the 

 turning-point in a reflex action is no doubt affected 

 by the condition which it receives from the sensory 

 and passes on to the motor nerve. But if we 

 imagine that in an act of consciousness the cor- 

 puscles of the hemispheres undergo any change 

 other than that of passing into the impressed con- 

 dition studied in nerves, we become guilty of an 

 assumption which has the plain objection of being 

 unfounded. That assumption is unfortunately 

 often made, apparently from confusion of ideas ; 

 for authors, particularly medical authors, speak as 

 if mental impressions lodged in the brain ; whereas 

 nervous impression, the only active condition into 

 which there is evidence of the brain passing, is 

 a physical state of a uniform nature, while, on the 

 other hand, a mental impression is the presence of 

 a notion in the mind, and the variety of such 

 notions is infinite. I shall return to the considera- 

 tion of the bearing of this remark on views as to 

 the details of the functions of the hemispheres, but 

 wish first to direct attention to the difficulties of 

 the received doctrine of sensation. 



I own that, even supposing all difficulties as to 



