342 BIOLOGICAL ASPECTS OF HUMAN PROBLEMS 



We may reasonably think of the human nervous 

 system as moulded, almost continually, by stimuli 

 arising mainly through the agency of other human 

 nervous systems. This powerfully moulding influ- 

 ence may be directly exerted, through speech and 

 behavior, but among cultivated peoples is effectively 

 reenforced by the indirect action of human records, 

 as by art, music, or literature. As these records 

 reflect the outer world of nature, as distinct from 

 man, it may be truly said that much of man's knowl- 

 edge of nature may come through human interpre- 

 tation of it in lieu of direct experience. It is, indeed, 

 a definite tendency of modern culture to exclude in- 

 creasingly the direct appeal of nature and to accept 

 as a substitute the experiences of other human beings 

 with respect to it. Hence we may say of cultured 

 races, at the present time more strongly than of any 

 other, that the progress and fate of their individual 

 members is in a high degree based on the neural 

 interactions of these members. We have already 

 seen that there is no satisfactory evidence of strict 

 spontaneity of action on the part of human nervous 

 systems or the individuals of whom they constitute 

 the essence ; but that, on the contrary, there prevails 

 an automatism of transcendent delicacy, refinement, 

 and complexity. This incomparable and superla- 

 tive automatism is the expression of the extreme 

 plasticity of the wonderful neural protoplasm which 

 makes up the nervous system of man. The experi- 

 ences of each human nervous system are so numerous, 



