cc-operation, have increased the efficiency of human living in any given 

 situation. But they have not necessarily ensured an adjustment of Hfe to the 

 balance of nature, so as to make the conditions continuously suitable for man. 

 It is indeed only in recent times that we have been aware of the underlying 

 balance of the plant and animal forms on which our own existence depends. 

 We can enlarge our population, we can lengthen individual life — but only to 

 a point. 



Life has endured for millions of years. But each individual has his little 

 day, and is gone. He gives way to others — to others of many different species 

 or to others of the same species — as he himself has been able to live only as 

 others have given way before him. 



602 



