LIFE AND EXPERIMENT 



attain the normal adult condition. By experiment we 

 attempt to ascertain the meaning of normally occurring 

 stages which are co-existing and successive, co-ordinate and 

 subordinate. We seek to unravel the tangle of the pro- 

 cesses or, from another point of view, to stem the rush of 

 developmental events in order to determine what in them 

 is cause and what effect. The picture that the normal 

 developmental process gives us must we trace In its every 

 line and shadow and by experiment aim to elucidate their 

 meaning. 



Hence, the method for the study of living systems is this : 

 to extend to the utmost a purely biological attack — that is, 

 to know qualitatively every process; to mark its beginning 

 and its end and in Its duration to map out most closely set 

 phases; to chart its course. This appreciation of the 

 normal life-processes will set the goal which we strive to 

 achieve by means of experimental attack. No matter how 

 far the experimental methods change normal condition and 

 behavior, always should results obtained with them have 

 bearing on the normal. The greater the extent of the 

 change, the more surely must we realize that it Is a change. 

 Conclusions drawn from greatly altered states concerning 

 the normal need most careful scrutiny. Death-changes 

 induced by experiment should be appreciated as such and 

 be considered as revealing the living condition, which 

 they extinguish. In no other way except by extinguishing it. 



Those experiments which alter a normal process least 

 have to-day especially great value in the study of the egg 

 and its development. Few investigators nowadays, I 

 think, subscribe to the naive but seriously meant compari- 

 son once made by an eminent authority in biology, namely, 

 that the experimenter on an egg seeks to know its develop- 

 ment by wrecking it, as one wrecks a train for understand- 

 ing its mechanism; he might also have said, as a young child 

 breaks up a watch to see the wheels go around. The days 



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