374 ZOOLOGICAL PHILOSOPHY 



nervous fluid, which, after having produced sensation, carries into 

 the intellectual organ the particular agitation which it derived from 

 that sensation, impresses on some part of it the characteristic outhnes 

 of its movement, and finally renders them perceptible to the individual 

 by transmitting their eifects to his inner feehng. 



The ideas formed on seeing a sky-rocket for the first time, on hearing 

 a Hon's roar, and on touching the point of a needle are simple ideas. 



Now the impressions which these objects make upon our senses 

 immediately excite in the fluid of the corresponding nerves an agitation 

 which is different in each case ; the movement is propagated to the 

 nucleus of sensations ; the whole system immediately shares in it ; and 

 sensation is produced by the mechanism that I have already explained. 



Thus, if our attention has prepared the way, the nervous fluid 

 instantly conveys the image of the object or some of its outlines to our 

 organ of intelhgence, and impresses that image or those outhnes on 

 some part of the organ ; the idea traced is then immediately carried 

 back by it to our inner feehng. 



In the same way that the nervous fluid by its movements is the 

 agent for carrying to the nucleus of sensations the impressions of 

 external objects that affect our senses, so too this subtle fluid is the 

 agent for conveying from the nucleus of sensations to the organ of 

 intelhgence the product of each sensation that is raised, for tracing its 

 outhnes there or impressing them on it by its agitations if the organ 

 has been prepared by attention, and for subsequently carrying back 

 the resultant to the individual's inner feehng. 



Thus, in order that the outhnes or image of the object which has 

 caused the sensation may reach the organ of understanding and be 

 impressed on some part of it, it is necessary that the organ should 

 first be prepared by an act of attention for receiving the impression, 

 or that this act should open the way by which the product of that sen- 

 sation may travel to the organ where the outhnes of the object may be 

 impressed : in order that any idea may arise or be recalled in conscious- 

 ness, it is necessary again by means of attention that the nervous fiuid 

 should convey its outhnes to the individual's inner feeling ; this idea 

 then becomes perceptible to him and may be recalled at the will of the 

 individual for a longer or shorter period. 



The impression which forms the idea is thus actually traced and 

 graven on the organ, since memory can recall it at the will of the 

 individual and make it perceptible once more. 



This in my opinion is the probable mechanism of the formation of 

 ideas ; the mechanism by which we recall them at will until time 

 has obliterated or blurred their outlines so that we can no longer 

 remember them. 



