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ANNALS NEW YORK ACADEMY OF SCIENCES 



such a series of measurements are most conveniently shown by plotting 

 the values of the voltage against the values of the current, one plotted 

 point representing the voltage and current obtained with a given re- 

 sistance (figure 4). It is found that the points lie near a straight line 



lOO . 



amperes 



Figure 4. Peak voltage vs. peak current in external circuits of different resistance joining elec- 

 trodes on main organs of Electrophorus. (From J. Gen. Physiol.) 



with both the electric eel and the electric rays.* The meaning of this 

 result is that the electric tissue, at least at the peak of the discharge 

 and within the uncertainty of the measurements, can be described elec- 

 trically in terms of electromotive force and ohmic resistance. 



If the external resistance were made negligibly small, the voltage 

 also would be negligible. The corresponding current, estimated by 

 extrapolating the straight hne of the graph to zero voltage, is the maxi- 

 mum current of the organs. This maximum current varies from one 

 specimen to another and, in Electrophorus, it varies between different 

 parts of the main organs. In an average specimen, around 1 m. in 

 length, it is about 1 amp. at the anterior end of the main organs. Values 

 of about 4 amp. have been found in adult specimens of Narcine 

 brasiliensis, and a value of 120 amp. was roughly estimated in a single, 

 very large specimen of Torpedo occidentalis.^' *• ^ 



These great variations are due more to differences in the cross-sec- 

 tions of the organs than to differences in the electrical characteristics 

 of the tissue. The maximum current per unit area of the electroplax 

 layer was found to have values in Electrophorus from .02 to .06 amp. 

 per cm.^, the average being about .04. In Narcine brasiliensis, the 

 value is about 0.1 and, in the specimen of Torpedo occidentalis just 

 mentioned, it was about 0.2 amp. per cm.^ (In this calculation and 



