1893.] on The Transmission of a Nervous Impulse. 95 



blows, (4) chemical reagents. To all these the nerve responded 

 better when cooled, though it transmitted the nerve impulse pro- 

 duced by such response with greater difficulty. To one agent only 

 did the nerve respond less readily when under the influence of 

 localised cold ; this was the induced electrical current. 



It thus appears necessary to reconstruct our view of the nature 

 of the process during nerve transmission, for the two events in the 

 nerve, the response to external stimuli and the power to transmit 

 such response, are affected in a diametrically opposed manner by 

 such a simple change as alteration in the nerve's temperature. The 

 favourable influence of localised cold on the response of excitable 

 tissues to external stimulation was further displayed by description 

 and demonstration of the effects produced when muscles, and not 

 nerves, were the objects of experiment. In all cases cold favoured 

 the capacity of the muscle to reply to the stimulus. 



Finally, the lecturer brought forward some observations which 

 appeared to show that in addition the transmitting power of a nerve is 

 largely affected by the nature of the agent which started the nerve 

 impulse. We have found it possible to arouse a nerve by a galvanic 

 current in two ways : (1) so that localised cooling of a portion of the 

 conducting path will favour the passage of the impulse (the normal 

 condition), and (2) so that the same localised cooling will block the 

 impulse. It would thus seem that nervous impulses, when started 

 on their journey along nerves, bear throughout that journey some 

 impress of the agent which started them, and hence, that the im- 

 pulses which are initiated by even slightly different physical agencies, 

 and are then transmitted along nerve-fibres, differ from one another 

 as regards the character of some fundamental quality. 



Professor Gotch concluded that these and other recent observa- 

 tions gave experimental proof that the property of transmission 

 possessed by nerves is correlated, not merely with that of excitability, 

 but largely with the source, and thus the nature of the impulse, so 

 that the unknown molecular changes which form the living basis of 

 such transmission in any one nerve-fibre are not the same for all 

 impulses, but change with the source of each. 



[F. G.] 



