Z>//^ a?id Experiment 



The method employed in the investigation of the 

 living thing, the foregoing statements clearly indicate, 

 must be different from that in physical sciences: the nature 

 of the thing investigated determines the method of inquiry. 

 Description is the method of most use in biology. It plays 

 a larger role here than in physics not because experimental 

 biology is a younger science than physics, as one often 

 avers, but because of the heterogeneity and complexity of 

 the composite life-unit. The more heterogeneous and 

 complex an object, its parts undergoing multitudinous 

 kaleidoscopic changes, the more important description 

 becomes. And when this object is minute, its changes 

 evanescent, accurate description is imperative. By 

 description the objects may be defined and the changes 

 recorded in more and more closely set stages. 



This statement, however, by no means implies that 

 experiment has no place in the study of the state of being 

 alive. Both description and experiment are utilized by 

 all the natural sciences — the extent to which each is 

 used being determined by the state of the matter investi- 

 gated. Just as the complex organization of living matter 

 demands the larger employment of description, so it 

 prescribes experimental method. The present chapter 

 aims to evaluate the place of experiment in the study 

 of a living thing in order to clear the ground for the dis- 

 cussion of the problems with which this book deals. Thus 

 I present my conception of the role of experiment in 



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