FRANK MORRELL 3S5 



which iUustrate the use to which our model of neural learning may be put. 

 The experiments involve the supposition that the molecular basis of 

 memory nnght be found within the cells or cell systems of the mirror 

 focus. 



Among the most important known determinants of membrane respon- 

 siveness is the distribution of charge across the cell boundary. While the 

 relative internal and external concentration of various ion species are 

 known to produce radical alterations in membrane potential, these changes 



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Fig. 10 

 Slighdy liitjhcr power phoroniicrograph thrmii^h region of nnrriir tocus. The 

 appearance of normal cortical cells with this method is seen in the lower right 

 and upper left hand corners. Methyl green pyronin stain. Magnification X 85. 



arc transient and it seems unlikely that distribution oi the relatively per- 

 meable free ions could account for lasting patterns in the intricate local 

 distribution of membrane potential. A much more likely candidate for 

 such permanent patterning is the configuration of potential set up in 

 ordered sequences of amino acids or proteins. Yet these substances, too, 

 are known to be in continual Bux, in generation, breakdown and re- 

 generation. One must postulate an organizer substance, a substance which 

 in its synthesis, breakdown and resynthcsis can perpetuate or regenerate 

 the same pattern of polarized molecular configurations which were 

 previously present. The search for an organizer substance leads one 



