362 THE GROWTH OF THE BRAIN. 



ever, of this utilisation of previous exertion exists only 

 where the machinery of civilisation is developed, for the 

 advantages which the descendants enjoy are mainly 

 expressed by relief from unnecessary and wasteful toil 

 and life in a more invigorating atmosphere. 



The effective power of a community, depending as it 

 does upon the subdivision of the labour within it, 

 and the mutual dependence of one part on the others, 

 and its trust in them, alone renders it possible for 

 any group of individuals to attend to its own affairs 

 with the necessary freedom from distraction. In- 

 dividualism, in the biological sense of self-sufficiency, is 

 the one necessary condition for uncivilised existence, 

 and so long as each member of the community is 

 concerned with the preparation for all emergencies, just 

 so long is he debarred from advance. 



If in any science a student were called upon to 

 develop his subject in theory and technique from the 

 very beginning there is no doubt that such a one 

 would acquire much useful mental exercise, but the 

 body of fact that to-day forms each branch of know- 

 ledge, and which furnishes ever-increasing data upon 

 which the logic of succeeding generations is to be 

 exercised, this body of fact, the stored efforts of 

 preceding workers, would be largely lacking, and we 

 should be limited to just so much of science as could 

 be obtained by one man in a long lifetime. 



The degree of interdependence is in some sense a 

 measure of the degree of civilisation, but because it has 

 proved marvellously useful to store in an available form 

 the results of the activity of our predecessors, it by no 

 means follows that by this act our own mental powers 

 have attained a greater vigour or a broader span. As 

 well measure the diligence of two farmers by the size of 

 their crops, when one has planted good seed in fertile 



