The Evolution of the Sciences 



We must therefore abandon the idea of finding 

 a characteristic and general definition of organic 

 irritability, though this irritability is one of 

 life's most characteristic features. The excited 

 muscle will contract so long as the tissues com- 

 posing it are alive ; as soon as they are dead its 

 contractility ceases. There is, however, another 

 less immediate, but more delicate, criterion of 

 life. The appearance of electric currents as 

 the result of excitation supplies a most sensitive 

 means of investigation, because our instruments 

 enable us to measure the feeblest currents with 

 precision. Mr Bose has had recourse to this 

 criterion, and the originality of his researches 

 consists in his having subjected to the same 

 experiments, with the same apparatus, inorganic 

 substances as well as animal and vegetable 

 tissues. 



The method generally adopted by Bose 

 consists in clamping firmly in the middle the 

 body to be experimented upon muscle, 

 vegetable or inorganic body and connecting 

 both its extremities with a very sensitive 

 galvanometer in a closed circuit. Any electric 



action taking place in the body will thus be 



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