380 Animal Life and Intelligence. 



may say, with Mr. Grant Allen,* that " the acute pains, as 

 a class, arise from the action of surrounding destructive 

 agencies ; the massive pains, as'* a class, from excessive 

 function or insufficient nutriment." But since massive 

 pains, when pushed to an extreme, merge into the acute 

 class, " the two classes are rather indefinite in their limits, 

 being simply a convenient working distinction, not a 

 natural division." "Massive pleasure can seldom or never 

 attain the intensity of massive pain, because the organism 

 can be brought down to almost any point of innutrition 

 or exhaustion ; but its efficient working cannot be raised 

 very high above the average. Similarly, any special organ 

 or plexus of nerves can undergo any amount of violent 

 disruption or wasting away, giving rise to very acute pains ; 

 but organs are very seldom so highly nurtured and so long 

 deprived of their appropriate stimulant as to give rise to 

 very acute pleasure." The amount of pleasure varies, 

 according to Mr. Grant Allen, whose discussion of the 

 subject is, perhaps, the best and clearest we have, directly 

 as the number of nerve-fibres involved, and inversely as 

 the natural frequency of their excitation. No doubt the 

 principles above sketched out are somewhat vague and 

 general ; but we are scarcely justified in formulating any 

 that are more precise and exact. 



Accepting now the theory of evolution, we may say, 

 furthermore, that during the long process of the moulding 

 of life to its environment, there has been a constant 

 tendency to associate pleasure with such actions as con- 

 tribute towards the preservation and conservation of the 

 individual and the race, and to associate pain with such 

 actions as tend to the destruction or detriment of the 

 individual or the race. For there can be little doubt that 

 pleasure and pain are the primary incentives to action. 

 Without the association of pleasure with conservative 

 action, and pain with detrimental action, it is difficult to 

 conceive how the evolution of conscious creatures would 

 be possible. Conservative action, if it is to be persisted 



* " Physiological .Esthetics : " chapter on " Pleasure and Pain." 



