326 ZOOLOGICAL PHILOSOPHY 



If I am pricked in the little finger of one of my hands, the nerve of 

 the part affected runs in its special sheath and without communica- 

 tion with others to the common nucleus, where it delivers the agitation 

 it has received ; this agitation is immediately propagated thence to 

 the fluid in all the other nerves of the sensitive system : then by a 

 true reaction or repercussion this agitation flows back from all points 

 to the common nucleus, where it produces a shock and a compression 

 of the agitated fluid on all sides save one. This total effect produces a 

 perception, the result of which is carried back by the single nerve 

 which did not react. 



In point of fact, the nerve which brought in the original impression, 

 and thus set up the agitation of fluid in all the rest, is the only one 

 which gives no reaction ; for it is the only one that is active while all 

 the rest were passive. The whole effect of the shock produced in the 

 common nucleus and passive nerves, as also the resulting perception, 

 must therefore be carried off by this active nerve. 



An effect of this kind resulting from a general movement throughout 

 the individual, necessarily advertises him of an event passing within ; 

 and this individual, though he cannot make out any details, derives 

 from it a perception to which he gives the name of sensation. 



The strength of this sensation is presumably proportional to the 

 intensity of the impression, and its character would correspond with 

 the actual nature of the impression received ; it appears to be produced 

 in the very part affected, simply because the nerve of that part is the 

 only one affected by the general disturbance that is set up. 



Thus every shock produced in the nucleus or centre of communica- 

 tion of the nerves, due to an impression received, is felt throughout 

 the body though always appearing to us to take place in the very 

 part which received the impression. 



With regard to this impression, there is necessarily an interval 

 between the moment at which it is made and that when sensation is 

 produced, but this interval is so short, on account of the rapidity of 

 the movements, that it is impossible for us to perceive it. 



Such, in my opinion, is the wonderful mechanism underlying physical 

 sensibility. Let me repeat that it is not matter that feels, for matter 

 has no such faculty ; it is not even a part of the individual's body, 

 for the sensation experienced in any such part is only an illusion, 

 as many facts combine to prove ; but it is a general effect, produced 

 throughout the body, which is entirely concentrated on the same 

 nerve that first caused it, and which is necessarily felt by the individual 

 at the extremity of that nerve where the impression was made. 



All that we perceive is within ourselves : this is now a well-estab- 

 lished truth. For a sensation to arise, it is absolutely necessary that 



