

Science tyro%te$$. 



No. 9. November, 1894. Vol. II. 



INHIBITION. 



OUR positive knowledge of inhibitory phenomena, and 

 still more our speculative forecasts, more or less 

 closely dependent upon such added knowledge, have of late 

 years greatly extended themselves. The term itself, first 

 used to denote the now familiar phenomenon of cardiac in- 

 hibition, has expanded far beyond its original clear bound- 

 aries, to include, not merely all cases where one positive 

 action is arrested by another positive action, but also 

 cases in which we had been satisfied to see mere cessation 

 of action or paralysis by defect. The familiar instance of 

 cardiac inhibitory nerves has led us to look for and find in- 

 hibitory nerve action wherever a tissue becomes less active, 

 and in the case of every cessation of action to see not 

 merely a fall of motor action but a rise of anti-motor action. 

 The need for some rational theory of inhibitory action in 

 the well-known case of the cardiac vagus, in the hardly 

 less well-known phenomena of vaso-dilatation, in the whole 

 range of nerve-centre phenomena, has led to doctrinal con- 

 ceptions apparently most disconnected from an experi- 

 mental base of departure, yet most provocative of experi- 

 ments made for the definite purpose of providing such 

 experimental base. The clear case of motor and anti-motor 

 cardiac and vascular nerves has invited us to admit as a 

 probable generalisation that all tissues are controlled by 

 excitatory and by inhibitory nerves. And explicitly or 



implicitly this generalisation has been operative in the most 



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