METHODS 79 



hood of a closed circuit develops in it an induction current 

 which tends to oppose itself to the displacement" 



Also to the more general Law of Le Chatelier a law 

 which has been given a complete exposition in the admir- 

 able work of Willard Gibbs : 



" In a system of bodies in the state of equilibrium, the 

 modification produced by the variation of one of the factors 

 of the equilibrium is of such nature that it tends to oppose 

 itself to the variation determining it." 



Here are two very general laws, both of extreme simplicity. 

 They owe their simplicity to the fact that they have been 

 established by the natural method which I propose and which 

 we are now to apply in the domain of biology. Doing 

 this, we are not guilty of novelty ; long since the wisdom 

 of the nations, without saying it in so many words, employed 

 a method so fruitful in results by the proverb Fit fabri- 

 cando faber that is, by often repeating an act you become 

 fitter to do it again. The modification introduced into an 

 organism by the repetition of a given operation cannot be 

 analysed chemically. But it is very simple to take the 

 operation itself as the reagent in the modification realized ; 

 through it we become fitter, habituated to live is to habituate 

 oneself. This is what the wisdom of the nations teaches us 

 and in its inexhaustible treasure Lamarck found his law of 

 habit " The function creates the organ." 



