10 



Vol. XXXVII., Art. ].-K. Fuji; 





/;;.','VW^-, 



-WAVWIT — ' 



Fig 2. Connection.« 

 of shutter. 



stimnlatiuii-appavatus. Tlie sliuttL']' docr^ not 

 work udIi'ss a ^lorse key k is pressed wliich 

 serves as a sliunt to tlie l)reak-circuit con- 

 trivance. By adjusting tlie ])hase of the break 

 witli reference to the drum, the shutter may 

 be opened when any desired position on the 

 fihïi comes to receive hglit from tlie oscillo- 

 graph. For the sake of economy of time and 

 of film, a series of discliarges are pliotograph- 

 ed m order on one hlin. liv tlius shifting the 

 phase of break with reference to the drum. 

 The shutter may l)e used as a time-shutter if 

 desh"ed, wlien it is connected to tlie ordinary 

 Morse key as sliowii in Fig. .*>. 

 T3efore describing the stimulation-apparatus, we sliall ex])]ain 

 the form of stimulus used in our experiments. The stimulation ordi- 

 narily used was an induced current in the 

 secondary circuit of a Du Bois Reymond's 

 induction coil usually employed by physi- 

 ologists. When the primary current is 

 suddenly opened , the secondary current 

 increases from zero to a maximum value in a very short pei-iod, 

 and then decreases exponentially to zero. By shunting the second- 

 ary current at a desired instant in its decreasing stage, it can be 

 made to decrease to zero suddenly. Such a current was ordinarily 

 used as our stimulus in direct stimulation. In many experiments 

 the strength and the duration of such a secondary stimulating 

 current were changed and their influence upon the discharge curve 

 was investigated. The oscillogram in .Plate I.( Fig. 2) shows a 

 form of such stimulus followed by the discharge current of the 

 organ in response to it. Here we may remark that we can see in 

 this oscillogram how well the shutter works. In the indirect 

 stimulation, however, the induced current caused by an instan- 

 taneous contact in the primary circuit of the induction coil is 

 ordinarily used. This forms a stimulus of very short duration as 

 shown in Fig. 4. For brevity we shall hereafter call such 



Fig. 3. Connection of Morse 

 key for time-shutter. 



