in FUNCTION OF MIND AND BRAIN 37 



mode of reaction, decides the way in which we take things 

 without our knowledge of its operation. Though a man 

 may in part know himself in the sense of being aware of 

 certain idiosyncrasies of temper and on his guard against 

 them, it is only science dealing with nerve and brain, here- 

 dity, education, and the reaction of body and mind that can 

 render in fully explicit terms the true nature and limits of 

 the hereditary factor. 



(5) Enough however will have been said to show that 

 the ground layer of mind is a property of the hereditary 

 structure. Upon this foundation experience works, but 

 the result at any moment is not to be severed by any 

 mechanical process into effects of experience and effects of 

 heredity. The result is the product of a continuous pro- 

 cess of interaction, and will accordingly be a function of 

 both the contributory factors. There is, however, one 

 element common to the two. The hereditary element is 

 itself shaped indirectly by the experience of the ancestral 

 stock. The stock has had to live and act within a world 

 of experience which is on the whole the same world, and 

 it has had to adapt itself to that world or perish. Hence,, 

 in the basis of the individual constitution lie tendencies, 

 modes of feeling, promptings of action making in the main 

 for sanity, making at least for the race preserving as against 

 the race destructive line of conduct. These tendencies 

 may be so precise and complete as to determine action 

 without the need of any individual experience to perfect 

 them. They then form the basis of inherited reflexes or 

 instincts. Or they may be vaguer and more general, and 

 may figure accordingly as promptings, tendencies, charac- 

 teristics, or mere potentialities which the experience of life 

 serves to define and complete. The first and more de- 

 veloped form plays the more important part in animal life 

 where the scope of consciousness is smaller. As the sphere 

 of conscious correlation grows so there is less room for 

 fully developed specifically determined modes of reaction, 

 and the function of the pre-existing structure is rather to 

 form a basis for correlations which are constantly effected 

 anew by fresh mental efforts. Hence, though the heredi- 

 tary equipment of man is not poorer but richer than that 



