NERVOUS ACTION 



attached two thin nicinl)ranes only a few microns thick. The whole 

 enzyme activity is in \hr sheath. The axoplasin is practically free of 

 choline esterase (1). 



Bioelectric phenomena occur at the surface. The localization 

 of the enzyme at the neuronal surface and the high rate of acetylcholine 

 metabolism make possible the assumption that the ester is connected 

 with the electric manifestations of nerve activity. But for the interpre- 

 tation of the actual role of acetylcholine in the mechanism of nervous 

 action the activity of the enzyme had to be connected with an event in 

 the living cell. Such a correlation has been established in experiments 

 carried out on the third and perhaps most valuable special case, viz-, 

 the electric organ o fish. 



Parallelism between Enzyme Activity and Voltage of the Nerve Action 

 Potential. The electric discharge in these organs is identical in nature 

 with the nerve action potential of ordinary nerves. The only dis- 

 tinction is the arrangement of the nervous elements, the electric plates, 

 in series. The potential difference developed by a single element is 

 about 0.1 v., which is the same order of magnitude as that found in 

 ordinary nerves. In the species with the most powerful electric organ 

 as yet known, Electrophorus electricus, the so-called electric eel, several 

 thousand elements are arranged in series from the head to the caudal 

 end of the organ. Thus, the voltage of a discharge amounts to 

 400-600 V. on the average; and, in some specimens, more than 800 

 V. have been observed. In Torpedo, another species with a powerful 

 electric organ, the elements are arranged in dorsoventral direction. 

 Since it is a fiat fish, the number of plates usually does not surpass 

 400 to 500; and, consequently, the discharge is only 30-60 v. on the 

 average. In the large Gymnotorpedo occidental is found on the North 

 American east coast, especially in the water surrounding Cape Cod, 

 the number of plates in scries and, consequently, the voltage may be 

 more than twice as high. 



In 1937, the electric tissue was introduced by the writer as 

 material for the study of the role of acetylcholine in the transmission 

 of the nervous impulse. A high concentration of choline esterase was 

 found in the strong electric organs of Torpedo and E. eleclricus. These 

 organs hydrolyze in one hour amounts of acetylcholine equivalent to 

 one to five times their own weight. In the larger specimens, the 

 organs have a weight of several kilograms, so that the amount of acetyl- 



