'2 HE BEGINNINGS OF LIFE. 45 



ment only of certain nerve-changes, or whether it is to 

 be regarded as the invariable and principal result of the 

 activity of the elements of a part which is to be looked 

 upon as the organ of Consciousness, there is still room 

 for doubt; there is, on the other hand, a certainty that 

 the various modes of Consciousness which may be 

 called into activity by any sets of nerve-changes are 

 not to be considered as correlatable with such nerve- 

 changes as a whole. c We have good reason to con- 

 clude/ as Mr. Spencer says, c that at the particular place 

 in a superior nerve-centre where, in some mysterious 

 way, an objective change or nervous action causes a 

 subjective change or feeling, there exists a quantitative 

 equivalence between the two : the amount of sensation 

 is proportionate to the amount of molecular transfor- 

 mation that takes place in the vesicular substance af- 

 fected. But there is no fixed or even approximate 

 quantitative relation between this amount of molecular 

 transformation in the sentient centre and the periphe- 

 ral disturbance originally causing it.' So that, as the 

 same writer also says l : c Between the outer force 

 and the inner feeling it excites, there is no such corre- 

 lation as that which the physicist calls equivalence 

 nay, the two do not even maintain an unvarying pro- 

 portion. Equal amounts of the same force arouse dif- 

 ferent amounts of the same feeling, if the circumstances 

 differ. Only while all the conditions remain constant 



1 ' Principles of Psychology,' 1869, No. 22, p. 194. 



