Kesoarches on the Discharge of the Electric Organ. ß5 



iv.) The electromotive force increases probably from zero 

 when the second stimulus separates more and more from the end 

 of the refractory period and when at a certain interv^al between the 

 two stimuli it Ijecomes even greater tlian tlie normal and then 

 decreases again. 



V.) The abnormal increase of the electromotive force may be 

 interpreted as the summation effect of the second discharge and 

 the secondary discharge of the first stimulus. 



vi.) The second discharge caused by two successive submaxi- 

 mal stimuli given at a point in the nerve may be superposed on 

 the first discharge, and the modal latent period of the second 

 discharge seems to be even smaller than the normal at a certain 

 interval between the two stimuli. 



vii.) The discharge l)y an oi)ening-stimulus given in the 

 nerve may l)e superposed on that by closing-stimulus. 



viii.) Phenomena vi. and vii. may give support for the 

 theory of "all or none," but for this we must assume new 

 subordinate properties ef the nerve which is worth while investi- 

 gating hereafter. 



VII. Fatigue phenomenon. 



Fatigue phenomenon was investigated in two different ways. 



(1) The registering drum Avas rotated very slowly by connect- 

 ing the shaft of it with the clockwork of a kymograph, and succes- 

 sive momentary stimuli about 25 in a second were given to the 

 nerve and the deviation oi the strip of the oscillograph was photo- 

 graphed on a film. The periphery speed of the drum being about 

 1 cm. per sec. , a discharge curve reduces to a straight line and the 

 locus of its summit forms the so-called fatigue curve. 



(2) The drum was rotated rapidly and two stimuli in each 

 revolution were given to the nerve so that tliey might be photo- 

 graphed at two fixed places on the film. The stimulus consists of 

 the induced current of an induction coil, which was caused by 

 the make and break of the primary current flowing for a very 

 short interval during which a peg on the shaft makes instantaneous 

 contact with a stationary conductor (Plate IV. , Fig. 1). The direc- 



