ELECTROKINETIC MECHANISM OF MINIATURE

of a single vesicle. We shall outline an electrokinetic model for this process consistent with present experimental data which indicate that lnv = f(T,P,E), where v is the frequency of MEPP's, T the absolute temperature, P the osmotic pressure of the fluid in the synaptic cleft, and E the polarization of the presynaptic membrane. While the model may not be unique in its consistency with the data, it incorporates electrochemical concepts which are shown to be quantitatively appropriate to this new subject matter. The normal frequency of MEPP's is 1 or 2 per sec, but Liley8 observed a marked increase in v with cathodic polarization and his measurements on rat-diaphragm preparations, as replotted by Katz,9 yielded the empirical relation dlnv/dE 1.63 X 102 [at 200C], where E is in volts. Our theoretical treatment is based on the theory of rate processes as applied to electrode phenomena.'0 Let us consider vesicles to be randomly approaching a