Il8 PHYSIOLOGICAL TRIGGERS 



coupling of these two components in the chemical-physical system that is the 

 functional membrane. The electrical capacity is a reservoir of energy which 

 can be delivered at almost any desired rate and stands in the membrane as 

 inexorable as a taut spring, gravity, thermal energy and a true justice. 



As was mentioned in passing, an ion mechanism — that of sodium— is slightly 

 greedy, and as the pressure on it to pass these ions is lessened, it asserts itself 

 and opens the gate wider. But as a little ion current comes from the condenser, 

 the potential provided to the sodium conduction control is diminished and the 

 ion current tends to increase. This combination thus has in it the essential 

 characteristics from which instability can arise. And, indeed, after passing 

 over the hump, the sodium is the victim of its own greed — the more it gets, 

 the more it wants; but it can do so only because the utterly orthodox capacity 

 stands ready, willing and able to gorge it, and at the same time modifying the 

 conditions to further increase the sodium's appetite for more ions until it is 

 satiated. 



Other analogies are equally as good. The increase of reaction rate with tem- 

 perature speeds the increase of temperature in an exothermic reaction and leads 

 to burning or explosion under conditions approaching adiabatic, whereas the 

 isothermal situation, although perhaps fast, is quite without critical properties. 

 The domino-on-end draws upon its gravitational potential energy to restore 

 it after a small tilt, while beyond threshold gravity hastens its fall to the table. 

 But in the absence of gravity, it merely maintains a prosaic initial displacement 

 or rotational velocity. The liar, the embezzler and the murderer may be rela- 

 tively restrained in their crimes against society so long as that society does not 

 react to force them into ever-increasing jeopardy with more frantic efforts to 

 protect themselves from it. 



So we find the electrostatic capacity and the ion control each rather well- 

 behaved and quite lacking in critical characteristics, as has been amply demon- 

 strated and overwhelmingly confirmed for a living nerve membrane. But in 

 combination they can, most fortunately, egg each other on to produce all of the 

 highly effective and spectacular characteristics of nerve performance. 



It is not, then, for electrochemistry to look for the basis of a trigger mecha- 

 nism, a metastable state or an explosive phenomenon in the ions and their 

 reactions at the membrane, if only because the problems are not these. Rather 

 must attention be directed to systems— of themselves entirely stable, com- 

 pletely continuous and fantastically non-linear— which can produce the vari- 

 ations of the ion flows at various membrane potentials, for which the very 

 beautiful experimental facts serve both as a guide and as a stern judge. 



