HARRY (IRUNDFEST I45 



synaptic membrane. Long term functional interrelations might, for example, 

 subserve such phenomena as memory, to which brief, but frequent transducer 

 activity might contribute determinants by its temporary increases of the 

 permeability of the membrane. However, this domain of interactions is still in 

 a purely descriptive state. 



m) Synaptic Transmission and Function. The electrogenic responses of the 

 nervous system immediately subserve lirst, the function of collecting informa- 

 tion, and then of effecting actions based on this information. The various 

 sensory transducers convert specific types of stimuli into a single generalized 

 form of response, the electrical, probably graded according to some function of 

 the stimulus intensity. This electrogenic activity can be propagated electro- 

 tonically, and thus pass on information, but only for short distances in the cell 

 before it is degraded in form and amplitude to such an extent that it no longer 

 would serve as intelligence. The solution of this problem developed by most 

 animals is similar to that adopted much later by long-lines telephone and tele- 

 graph engineers — the insertion of amplifiers to make up for the losses. The 

 specific form used in living organisms is, however, much more elegant in its 

 apparent economy, although, as has been described here, in actuality is de- 

 pendent on much more complex phenomena. It has inserted, in the form of 

 all-or-nothing, electrically excitable membrane, combined trigger and ampli- 

 fier mechanisms more or less uniformly distributed along the cell, and thereby 

 capable of propagating information along the full extension of the cell. How- 

 ever, the triggered all-or-nothing response, while making available the precision 

 of that type of information,^" does not in isolation provide the nuances of which 

 graded responsiveness is capable. In many cells this weakness is overcome by 

 repetitive discharge of all-or-nothing spikes in a latency-frequency-number 

 code. Transmission of this information to the post-junclional cell again initiates 

 in the latter a graded response, more or less proportional to the information 

 coded in the message of the prejunctional unit, and this response in turn may 

 initiate activity suitable for propagating information or commands to another 

 junction. This is a complex mode of action, but it achieves its ends with an 

 economy of means at hand, ionic asymmetries, resting membrane potential, 

 and a membrane of high resistivity, but probably also of extremely high com- 

 plexity in its molecular structure and in the adaptations of this to the many 

 demands of the organism. 



SUMMARY 



Trigger mechanisms of electrogenesis operate on the substrate of the resting 

 polarization of the cell. The latter is probably complexly produced because of 



10 Von Neumann (153) has made the illuminating analogy between all-or-nothing re- 

 sponsiveness and the digital computer, and between graded, decrementaily propagated 

 responsiveness and the analog computer (cf. also isa). 



