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ANNALS NEW YORK ACADEMY OF SCIENCES 



(a) 



(b) 



(c) 



(d) 



Figure 6. Graphs of spatial distribution of potentials on the outer and inner sides of post- 

 synaptic membrane, the synaptic region being in center, i.e., potentials are ordinates and dis- 

 tances abscissae. The reference potential is given by a distal region of the membrane, the outer 

 side being shown above the inner. The normal resting condition is shown by the broken lines 

 separated by the resting potential, (a) Initial Ai focus at synapse with low intensity cathodal sur- 

 round, (b) Reversed phase with C2 synaptic focus and anodal surround (cf. figure 5b). (c) 

 Membrane potentials, when external field generated by pre-synaptic impulse is removed, the 

 spatial distribution of the potentials across the membrane being identical with those of (b). 

 (d) Potentials after generation of local response at synapse, with the catelectrotonus (the synap- 

 tic potential) spreading thence over the post-synaptic membrane. Hatched area shows specialized 

 synaptic zone of membrane. Impulse initiation occurs outside this zone, for example at the arrow. 



There would be no synaptic potential, with its characteristic long 

 duration. 



The additional assumption (part 4, C) is necessary, in order to ex- 

 plain the origin of the synaptic potential. It postulates that, when 

 above a critical intensity, the cathodal focus evokes at the synaptic 



