THE INSTINCT OF SURVIVAL 111 



of human individuals, it is clear that there are dis- 

 tinctive peculiarities in the expression of this instinct 

 at different ages which exhibit a definite dependence 

 on the biological attributes. The helplessness and 

 vague consciousness of infancy is succeeded by the 

 improved attentiveness and better motor control of 

 childhood with its seemingly inexhaustible supply 

 of reserve nervous energy. The rapid growth of 

 infancy and childhood, like the still more rapid 

 growth that occurs in the womb, depends upon an 

 extremely abundant supply of nutriment in the 

 former case as food, in the latter, from the mother's 

 blood. The rate of growth, both of body and brain, 

 is somewhat less during adolescence and early adult 

 life, when the growth of the sexual glands intrudes 

 upon the physiological processes in such a manner 

 as to stir consciousness with sexual feeling and thus 

 heighten a growing self-consciousness which is liable 

 to express itself through overconfidence and other 

 manifestations of crass egotism. In early adult 

 life, the elements of character are well determined, 

 yet sufficiently plastic to be significantly molded by 

 the forces of education. The struggle for a living 

 is intense at this period, for the average man, and 

 makes him view his rivals and opponents with sus- 

 picion, and the eagerness to succeed too often causes 

 him to deal harshly and inconsiderately with those 

 who stand in his way. Physical vigor is now at its 

 height, and the capacity for sustained mental and 

 physical exertion is notably great. This early adult 



