GROWTH n 



main quiescent for months or years be- 

 fore they start to grow. 



Hence it seems possible to have life 

 without growth and growth without life. 



Our analysis of the process of growth 

 illustrates the method which biological 

 investigation must very commonly pur- 

 sue. The biologist wishes to study living 

 matter in the same manner that the 

 chemist and physicist study their mate- 

 rial. His first task is observation, after 

 that he must analyze in order to discover 

 what properties are essential and what 

 are merely accompanying phenomena. 

 He need not attempt to explain these 

 phenomena, for, after all, we can never 

 arrive at ultimate explanations. But he 

 can attempt to predict and control. The 

 physicist cannot explain electricity but 

 he can predict and control electrical phe- 

 nomena. In the same way the biologist 

 hopes to be able to predict, and control 

 life phenomena. One method which he 

 finds particularly useful is to make arti- 

 ficial imitations which closely resemble 



