386 PROTOPLASMIC ACTION AND NERVOUS ACTION 



acid there is a P.D. of about 0.7 volt; a local current 

 flows between the two areas as indicated in Figure 3 

 (p. 253), the active area being anodal/ This current is 

 most intense near the active-passive boundary, because 

 the resistance of the portion of current traversing the 

 surface at any point in the passive area increases with 

 the distance of that point beyond the boundary; this 

 resistance depends chiefly on the length and specific 

 conductivity of the column of electrolyte intervening. 

 Up to a certain critical distance, s, beyond the boundary 

 the current wfll have sufficient intensity and local 

 density to reduce the film; hence the time, /, required 

 for the current to reach this intensity and the distance, 

 s, from the boundary are the essential variables to be 

 considered.^ The effect of increasing the resistance of 

 the local circuit (and thus decreasing the distance, s) 

 may be shown quaUtatively by suspending the passive 

 wire vertically, with a thin layer of acid adhering, and 

 then touching it below with zinc.^ Under these condi- 



velocity of transmission in nerve, introducing as factors the relative 

 electrical resistances of axone and sheath and the specific electrical 

 sensitivity of the tissue, as well as the rate of development of the electric 

 variation. If certain reasonable assumptions are made, this formula 

 agrees well with observation. Cremer's formula is consistent with the 

 foregoing sunpler expression, V = Ks/t, but attempts to define more 

 closely the conditions determining the value of 5 (Ber. ges. Physiol., II 

 [1920], 166; also Cremer's Beitrdge zur Physiologic, II [1922], Heft i, 31). 



* Jour. Gen. Physiol., Ill (1920), 130. 



' Only the maximal distance from the boundary at which the current 

 is effective need be considered, since both systems react in the "all 

 or none" manner. This type of reaction is a necessary condition for 

 indefinite transmission without decrement. 



3 It may also be shown quantitatively by inclosing the wires in glass 

 tubes of different diameters; the rate varies directly with the sectional 

 area of the tube. 



