NA TURE OF SENS A TION. 1 5 5 



through adjacent parts are put in motion, and, as he says, 

 " so made to supply oxygen and food with greater rapidity" 

 but this is a mere assertion on his part. If sensibility is 

 due to mere movement, Mr. Spencer ought to explain to 

 his reader what there is peculiar in the particular movement 

 associated with or followed by sensibility. Movement, 

 assimilation, and oxidation, will not necessarily give rise to 

 sensibility, nor is the latter invariably associated with these 

 phenomena, which may possibly have nothing special in 

 connection with sensibility. In these discussions actions 

 occurring in highly complex organisms have not been care- 

 fully distinguished from actions in simple living matter. 

 Sensibility, sensation, and feeling, remain undefined and 

 unexplained. 



Nor, I venture to think, can we hope to acquire an 

 accurate conception of the nature of (nerve) " sensation " of 

 the highest order, while we continue to be ignorant concern- 

 ing the exact change which takes place when (nerve) " sen- 

 sation," of the very simplest kind, is experienced. The 

 " sensation " is not a simple alteration in the position of 

 molecules of matter within us effected by material forces 

 outside us, but it is a change which results from the action 

 of something external to us upon an already formed 

 mechanism or apparatus, the structure and mode of action 

 of which has not been determined, but which we know was 

 constructed with us, and grew as we grew, and parts of 

 which are in some very intimate relationship (the nature of 

 which is unknown) with the most highly developed part of 

 our nervous system. We may know all about the external 

 something, we may know a good deal concerning the 

 general structure of the already formed internal apparatus, 



