402 ANNALS NEW YORK ACADEMY OF SCIENCES 



chemical data. Of particular importance is the fact that the line 

 correlating the two variables apparently goes through (figure 2). 

 This indicates a direct proportionality. The results are consistent 

 with the concept that the physical and chemical processes recorded are 

 directly associated and, consequently, interdependent.^^ Such a par- 

 allelism has not been found with other compounds or enzyme activities 

 known to be connected with nervous action. 



The direct proportionality found between physical and ch,emical 

 events is significant, in view of the changing morphological structure 

 of the electric unit, the electric plate. If all plates were identical in 

 structure, as e.g., in the case of the electric organ of Torpedo, the volt- 

 age and the cholinesterase activity would be expected to be directly 

 proportional to the number of plates. The situation is entirely dif- 

 ferent in the electric organ of Electrophorus electricus, because the 

 structure of the plates shows enormous variations. In spite of all 

 variations of the visible structure, the voltage of each plate is the 

 same, namely, close to 100 millivolts. It has, therefore, to be assumed 

 that the "active membrane," with which the electric manifestations 

 are connected and which is not yet well defined, does not change, but 

 is similar in all plates. The direct proportionality found between 

 voltage and enzyme activity suggests, then, that the physical and chem- 

 ical events may be associated with the same membrane and that they 

 may be functionally interdependent. Here again, the fact is important 

 only in connection with the great number of other observations, espe- 

 cially the extraordinarily high speed of the chemical process, without 

 which the correlation observed would not have the same interest. 



Two assumptions appear possible concerning the manner in which 

 ACh may act: It may produce electromotive force directly by action 

 on the surface, or it may decrease the resistance by increasing the 

 permeability of the boundary. Resistance and electromotive force 

 are closely related properties. So far, the evidence from experiments 

 on nerves is in favor of a change in resistance and increased perme- 

 ability. On the basis of alternating current impedance measurements 

 carried out on the giant axon of squid, Cole and Curtis calculated that 

 the resistance drops during the passage of the impulse from 1,000 ohms 

 to about 25 ohms per square centimeter.^^ In experiments on the elec- 

 tric tissue, a comparable drop in resistance was found by Cox, Coates, 

 and Brown. 2° There is no conclusive evidence that electromotive force 

 is actually produced during the passage of the impulse. One possible 

 interpretation on the basis of the material available at present is, there- 

 fore, the assumption that the parallelism found between voltage and 



