Life and Protoplasm -13 



servation may be somewhat indirect, involv- 

 ing complex instruments and calculations, 

 but the scientist must never be guilty of 

 weighting the data in favor of his precon- 

 ceptions. A current hypothesis or theory may 

 serve to indicate an area where further ob- 

 servations are needed and to determine the 

 nature of the needed experiments, but it 

 must never be allowed to warp the observa- 

 tions. 



2. Interpretation. The second step in the 

 research technique is to formulate a logical 

 explanation of the observed data. This in- 

 volves setting up a tentative hypothesis. The 

 hypothesis is usually broader than the data 

 from which it is induced, and consequently 

 the hypothesis must remain tentative until 

 further observation either confirms or denies 

 its validity. 



3. Prediction. This third step of the scien- 

 tific method requires that predictions be de- 

 duced from the working hypothesis. On the 

 basis of such predictions new experiments 

 are suggested for testing the hypothesis in 

 question. If the predictions are verified by 

 the experiments, the hypothesis is strength- 

 ened; if not, the hypothesis must be modified 

 or discarded. 



4. Experimentation. Each experiment is 

 calculated to test the predictions that are 

 deduced from a particular hypothesis. The 

 experiment is so designed that it yields a sin- 

 gle answer regarding the prediction in ques- 

 tion. Accordingly, each experiment must be 

 accompanied by a control in which all of the 

 factors, except the one being investigated, 

 are duplicated in the strictest possible 

 fashion. 



Experimental Control. Assume, for example, 

 that it is necessary to test a simple hypothesis: 

 that the loss of consciousness experienced by 

 an aviator at high altitude depends upon a 

 scarcity of oxygen. To prove this, it is neces- 

 sary to subject the aviator to an experiment 

 that rules out all other possibilities. At high 

 altitude not only is the oxygen scarce, but 

 the total atmospheric pressure and the tem- 

 perature are greatly reduced. Moreover, there 



may be accelerations and decelerations in the 

 speed of flight. Therefore, to decide the issue, 

 it is necessary to set up a control experiment, 

 utilizing a plane equipped with a pressurized 

 cabin, in which the temperature, the compo- 

 sition of the atmospheric gases, and other 

 factors can be regidated. In the control ex- 

 periment, the temperature and total air pres- 

 sure would have to be lowered to the level 

 indicated by the altitude in question, while 

 at the same time the available oxygen would 

 be maintained at the normal value, and the 

 velocity of flight and other conditions would 

 be the same as when the original blackout 

 occurred. Under these conditions conscious- 

 ness would not be lost. Consequently it could 

 be concluded that the hypothesis was sound, 

 and that unconsciousness does in fact depend 

 upon a scarcity of oxygen. 



Hypothesis, Theory, and Principle. The scien- 

 tific method may be illustrated more com- 

 pletely by considering an early hypothesis — 

 as to the nature of combustion , or burning. 

 This phlogiston hypothesis held favor prior 

 to the discovery of oxygen by Lavoisier in 

 1776. 



The phlogiston hypothesis held that com- 

 bustible material, such as wood, contains an 

 unknown gaseous substance, called phlogis- 

 ton, which begins to escape as soon as a ma- 

 terial is heated sufficiently to begin burning. 

 The hypothesis was based upon certain ob- 

 servations: something (the flame) appears to 

 escape from the burning body, and the ash, 

 or remnant of combustion, usually has a 

 lesser weight than the unburned material. 

 But one deducible prediction of this hypoth- 

 esis is that every material must be lighter 

 after burning; and this prediction cannot be 

 verified by all experiments. Some materials, 

 such as magnesium, i.e., the foil which burns 

 with glaring speed in a photographic flash- 

 light bulb, show an increase of weight after 

 combustion. The ash, magnesium oxide 

 (MgO), is significantly heavier than the un- 

 burned magnesium (Mg). In view of such ex- 

 ceptions, it became necessary to discard the 

 phlogiston hypothesis. Then, with the discov- 



