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ANNALS NEW YORK ACADEMY OF SCIENCES 



A. The Electrical Properties of the Surface Membranes and the 



Changes Produced by Catelectrotonus, Anelectrotonus, 



Local Responses, and Propagated Impulses 



Quantitative measurements liave been made of resistance, electro- 

 motive force, capacity, and rectification. The great diminution of the 

 two former during the excited phase of the impulse has been described 

 for nerve and muscle, vertebrate and invertebrate.^' ^^' "' ^^' ^^' ^^' **'' *'' 

 There is no good evidence that the large inductance of cephalopod 

 nerve^"' ^* is present in normal vertebrate nerve or muscle. The phe- 

 nomenon of para-resonance is simply explained in terms of the two 

 excitation constants of nerve.* In contrast with cephalopod nerve, 

 there is, in frog muscle, no appreciable lag between a sudden change 

 in potential and the associated change in the resistance of the mem- 

 brane.*^ Such a lag in cephalopod nerve has been attributed to the 

 large membrane inductance.^- On present evidence, vertebrate nerve 

 and muscle may, therefore, be regarded as having a negligible induc- 

 tance, and may be provisionally schematized, as in figure 1. 



Figure L Diagram showing probable electrical characteristics of ner/e and muscle membranes, 

 rx and n being, respectively, the external and internal longitudinal resistances ; C, E, and R, the 

 capacity, battery, and resistance of the membrane. 



B. Local Responses 



All grades of active local responses, short of propagated, all-or- 

 nothing impulses, have been shown to exist in nerve and muscle,^' ^''' ^^' 

 44, 4G, 47, 52, 70, 79 q^^^ jjj^y j^g explalucd as due to the limited area ex- 

 cited"® and/or to the low intensity of the excitation. ^^ In refractory, 

 anesthetized, or deteriorated nerve or muscle, these local responses may 

 be very large.*^' *'■ ®^' ^°' ''^ It appears probable that active local re- 

 sponses differ from passive electrotonic changes (including rectifica- 

 tion), jiist as with the propagated impulse, in that they are caused by a 

 temporary diminution, extinction, or even reversal, of the membrane 

 battery.^' i^' "• '^ 



* Katz, B.«: 28. 



