496 ANNALS NEW YORK ACADEMY OF SCIENCES 



measurements at later instants are steeper than the graph of the peak 

 values, indicates a rise in the internal resistance r, after the peak is 

 passed. 



These results led us, earlier, to suppose that the electromotive force 

 might be constant throughout the impulse and between impulses as 

 well, the discharge being caused by a transient drop in the resistance 

 from a very high resting value.' At that time, we had not succeeded in 

 plotting graphs of voltage and current at instants during the brief 

 interval of rising voltage. Both the steepness of the rising phase of 

 the oscillographic trace and its consequent faintness in the photo- 

 graphs made measurement difficult in this interval. Measurements 

 which we have made more i-ecently iiave obliged us to reconsider our 

 earlier opinion. The graphs of voltage and current obtained from 

 measurements during the interval of rising voltage do not meet at a 

 point. Moreover, even during the interval of falling voltage, we find 

 that deviations, which were formerly within our estimated errors of 

 measurement and which we, therefore, supposed were accidental, ap- 

 pear consistently in the later observations. 



The variation in resistance during the interval of falling voltage 

 seems, in any case, well established. It seems probable, also, that the 

 electromotive force is at least approximately constant during this phase. 

 Our immediate object is an estimate of the total electric energy pro- 

 duced in an impulse. Fortunately for this purpose, the time after 

 the attainment of peak voltage is most of the duration of the impulse. 

 Although the changes in the electrical characteristics, during the brief 

 phase of rapidly rising voltage, remain uncertain, the assumptions made 

 about them in the calculation of the energy can be varied widely, with- 

 out changing the result by more than about 10 per cent. 



From the equations already given, it follows that the current i 

 traversing the electric tissue is related to the current /, measured in 

 the external circuit by the equation : 



7 = (1 + R/R/)r. 



In this equation, E is known, and R' is determined by the intersection 

 of the voltage-current graphs. Thus, the current in the electric tissue 

 is found. 



The charge q which passes through the tissue in one impulse is 

 given by : 



q = jidt, 



where t denotes the time, and the integration is performed over the dur- 

 ation of the impulse. The integration can easily be done graphically. 



