INTRODUCTION. 
17 
so habitual in the course of generations that all the 
individuals of tie same species automatically perform the 
same actions under the stimulus supplied by the same 
appropriate circumstances. Eational actions, on the other 
hand, are actions which are required to meet circumstances 
of comparatively rare occurrence in the life-history of the 
species, and which therefore can only be performed by an 
intentional effort of adaptation. Consequently there arises 
the subordinate distinction to which I allude, viz,, that 
instinctive actions are only performed under particular 
circumstances which have been frequently experienced 
during the life-history of the species; whereas rational 
actions are performed under varied circumstances, and 
serve to meet novel exigencies which may never before 
have occurred even in the life-history of the individual. 
Thus, then, upon the whole, we may lay down our 
several definitions in their most complete form. 
Keflex action is non-mental neuro-muscular adjust- 
ment, due to the inherited mechanism of the nervous 
system, which is formed to respond to particular and often 
recurring stimuli, by giving rise to particular movements 
of an adaptive though not of an intentional kind. 
Instinct is reflex action into which there is imported 
the element of consciousness. The term is therefore a 
generic one, comprising all those faculties of mind which 
are concerned in conscious and adaptive action, antecedent 
to individual experience, without necessary knowledge of 
the relation between means employed and ends attained, 
but similarly performed under similar and frequently re- 
curring circumstances by all the individuals of the same 
species. 
Reason or intelligence is the faculty which is concerned 
in the intentional adaptation of means to ends. It there- 
fore implies the conscious knowledge of the relation be- 
tween means employed and ends attained, and may be 
exercised in adaptation to circumstances novel alike to 
the experience of the individual and to that of the species. 
