EXPERIMENTAL 125 



quest and I have ventured even on hypothesis. Experiment is 

 shortly defined by Jevons as observation plus alteration of con- 

 ditions. He points out that when we make an experiment we more 

 or less influence the events which we observe, as when we bring 

 together certain substances under various conditions of temperature, 

 pressure, electric disturbance or chemical action and so on, and then 

 record the changes observed ; and, that experiment may be of 

 two kinds, experiments of simple fact and experiments of quantity. 

 It is unnecessary here to describe all the rigorous rules that the 

 man of science so rightly imposes upon himself before he claims to 

 have proved his hypothesis, merely adding that among others he 

 requires, Exclusion of Indifferent Circumstances, Simplification 

 of Experiments, Removal of Usual Conditions, Removal of Inter- 

 ference of Unsuspected Conditions, Blind or Test Experiments. 

 Negative Results of Experiment, and he lays down the limits of 

 experiment. Those who have not for themselves investigated 

 some scientific problem may learn from this statement some of the 

 difficulties of the work of scientific men and will not fail to respect 

 and admire the caution, patience and honesty of the scientific worker, 

 and will perhaps feel the more gratitude to a class of men by whose 

 self-denying labours they live and move and have their being in a 

 modern state, and by whose discoveries, thus established, they are 

 frequently preserved from premature death. 



Experiments for the Present Purpose, 



Now in the matter of experiment for the proof of the thesis 

 that changes in the habits of an animal cause the changes observed 

 in their hair, it is at once seen that, ex hypothesi, no one can impose 

 and work with such calculated conditions as are ordained by 

 experiment, strictly so-called. The action of a habit is a slow 

 process and the movement of a hair is slow ; moreover the lifetime 

 of a man is too short and that of a horse, for example, too long to 

 allow of any individual experimenter applying artificial pressure 

 through many generations of horses, so as to be able to verify his 

 assertion that the effects of artificial pressure do what is claimed, 

 and that these effects are transmitted from one generation of horses 

 to another. One can conceive a calculated experiment of the kind 

 made with numerous individual rats, and successive generations, 

 but it is hardly likely that effectual pressure could be applied to 

 the hairy coats of such small and elusive mammals as would serve 

 to test the hypothesis. 



