ELECTRICAL FISHES 



435 



being led through wires to the galvanometer circuit, which includes 

 the frog-interrupter (6r n ). Two copper electrodes (EE^) are 

 further placed in the frog-trough, their wires being connected with 

 the muscle (6^) of the frog- alarum and (G u ) of the frog-interrupter. 

 The first was directly excited, owing 

 to the force of the shock from the 

 gymnotus, the last indirectly, from 

 the nerve, by means of the exciting 

 reed. " With the reverser placed as 

 in the figure, the lever of the inter- 

 rupter forms p#rt of the experimental 

 circuit. The arrows show the direc- 

 tion of current. With the reverser 

 turned over, the lever makes the shunt 

 circuit ; this distribution of current 

 corresponds with the dotted arrows." 

 Gotch has recently employed 

 another and widely applicable method 

 in his numerous experiments in time- 

 measurement on the torpedo. The 

 apparatus is essentially modelled after 

 du Bois-Keymond's spring-myograph. 

 Three contacts (K l K^ K s ), which are 

 opened in succession by the trigger, 

 were connected as in Fig. 275. K^ 

 opens the primary circuit of an in- 

 duction coil, the break shock being 

 passed into the nerve of an organ- 

 preparation. A corresponding part 

 of the discharge that follows acts 

 upon the galvanometer when the 

 opening of K^ abolishes a shunt to 

 the galvanometer circuit. Lastly, 

 the latter is permanently opened 



(by JT 3 ), so that the discharge from the organ only acts upon the 

 galvanometer for the period between the opening of K 2 and K^. 

 The trigger shoots past so rapidly that this interval may be 

 reduced to O'OOl". Hence if K. 2 is opened O'Ol" after K v 

 while K^ is gradually withdrawn from K^ the effect on the 

 galvanometer will be perceptible T tjJo" a ^ ter tne stimulation 



\ 



FIG. 274. 



