The Experimental Method 9 



plays in the result unless he study the effects of each under 

 different conditions that can be controlled. Little by little, in 

 this way we can hope to gain a clearer insight into the condi- 

 tions that, taken all together, produce the result. 



So much for the experimental method. It is pertinent to ask 

 what is an experiment? If I cut an earthworm in two to see 

 what will happen, have I performed an experiment ? Perhaps 

 not, for the actual performance of cutting the worm in two is 

 not the essential point. The essence of an experiment is a trial 

 or test, and the conditions are so arranged that an answer is ex- 

 pected. If the worm is cut in two in order to study the physio- 

 logical behavior of the two ends, as has been done in fact, with 

 some interesting results, or in order to see what regenerates at 

 the two cut ends, we have a distinct purpose in view, although no 

 formulated problem. If we proceed farther and remove a 

 definite number of segments in order to see how many come 

 back, and then try to determine what conditions are involved 

 in the results, we are clearly carrying out an experiment with a 

 more definite aim. This illustration will serve to show that the 

 most essential feature of an experiment is the anticipation of 

 the results of a test. The operation may be so simple, and the 

 conditions so Httle known, that to call the performance an 

 experiment may easily expose one to the ridicule of those un- 

 favorably inclined to the claims of experimental work. If the 

 process is carried out with scarcely a thought as to its purpose, 

 and in complete ignorance of all the conditions entering into 

 the problem, it can scarcely be called an experiment at all. At 

 most it is only a preliminary testing of possibilities. Much of 

 the pioneer work in experimental zoology has necessarily been 

 of this kind, and crude as such prehminary work must be, it 

 should be looked upon only as the first step toward a further 

 and more critical analysis. 



The carrying out of an experiment implies the formulation of 

 a working hypothesis, and this usually presupposes some knowl- 

 edge of the possible conditions that control the phenomena. 

 The experimental work becomes more exphcit and accurate the 



