"Life is an example of the way in which an energy-system 

 in its give and take with the energy-system around it can con- 

 tinue to maintain itself for a period as a self -centered, so to 

 say, self-balanced unity. Perhaps the most striking feature of 

 it is that it acts as though it * desired ' to maintain itself. ' ' 



— C. Sherrington : Man on His Nature, 

 p. 84; Cambridge, 1941. 



