2i8 PROTOPLASMIC ACTION AND NERVOUS ACTION 



bility of protoplasmic processes, including growth, to 

 electrical influences seems to imply that the electrical 

 conditions existing at these interfaces are an essential 

 factor in the control of these reactions. 



The general subject of the catalysis of substances 

 in aqueous solution in heterogeneous systems has thus 

 an intimate bearing on the fundamental biological 

 problem which we are considering; and a brief review 

 of the more relevant facts in this field is essential to the 

 further analysis of the conditions in living protoplasm. 

 It must be remembered, however, that the theory of 

 catalysis is still in many respects incomplete, and that 

 many reactions in living protoplasm appear to be 

 determined by other than purely catalytic conditions — 

 using the word catalysis in the accepted sense of an 

 acceleration in which the catalyzer undergoes no perma- 

 nent change in the reaction. Induced reactions probably 

 play an important part; and there are apparently also 

 cases where the catalyzer acts by introducing a factor 

 necessary to those special physical conditions — e.g., 

 flow of electric current through the bioelectric circuit — 

 which control the reaction. 



The general parallel between the conditions deter- 

 mining chemical reaction-velocities in general, and those 

 determining the flow of an electric current through a 

 circuit, has often been dwelt upon.^ The quantity of 

 material transformed in a reaction, or of current flowing 

 through the circuit is determined: (i) by the intensity 

 of a physical condition, called electrical or chemical 



^ Cf. Moore, Recent Advances in Physiology and Biochemistry^ 

 pp. 45 ff.; Mellor, Chemical Statics and Dynamics, p. 25; van't Hoff, Vor- 

 lesungen, I, 172, 178; Bredig, Ergehnisse der Physiol. ., I (1902), 137. 



