4 1 4 Additional Notes. 



like the fibres on which it acts, the supposition of Its existence 

 will not render at all more explicable the phenomena of mus» 

 cular contraction. For the sensorial power between the parti* 

 cles of a fibre is in contact with those particles, or it is not. If 

 it be, then the particles of the fibre cannot approximate, be- 

 cause there is no vacant space, and the sensorial power is not 

 penetrable. The whole fibre, with its sensorial power, forms 

 one connected substance, and is thence incapable of motion. 

 But if the sensorial power be not in contact with the partlcles^ 

 of the fibre on which it acts, it will be necessary to suppose the 

 existence of another intermediate agent (a subtle Jluid no 

 doubt), as we are repeatedly assured that nothing can act 

 where It does not exist. 



The doctrine of association is an important part of Dr. Dar- 

 win's theory J but upon the principles of this theory association 

 is impossible. Association is a particular quality or state of 

 sensorial power j but this power, or, which is the same thing, 

 the spirit of animation, is in a perpetual state of flux. It is 

 constantly secreted and expended, being too subtle to remain 

 any length of time in the system. The particles of this spirit, 

 then, cannot form any habitual connections or associations with 

 each other, because, in the very act of association, they are ex- 

 pended and destroyed. According to any laws of matter with 

 which we are acquainted, they can only be connected by means 

 of repeated simultaneous action ; but in their first action, ac- 

 cording to this theorist, they expire, and their places are sup- 

 plied by new partlcks, which, like them, can only act once 

 and fly off. The fibres, indeed, remain amidst this continual 

 flux of the vital fluid j but without it they possess no other 

 quality than those of inanimate matter. 



Once more; Dr. Darwin allows that stimuli sometimes 

 exist in contact with sensorial power, without producing cor- 

 responding effects. He accounts for this fact by supposing 

 that, from the inconvenience of obeying certain irritations, we 

 learn to suffer the stimulating material to accumulate till it 

 disagreeably affects us, and that the subsequent action is then 

 in consequence of this disagreeable sengaLion. But this is in- 



