OF THE ELECTRICAL ORGAN OF TORPEDO MARMORATA. 
527 
to be prolonged in character, like the after-effect which follows the nerve-organ 
response. Its duration and rate of subsidence were investigated in the same way as 
the latter had been, by closing the galvanometer circuit for 15" after excitation, 
opening it for 15", re-closing it for 15", &c. The readings of the deflections obtained 
in four experiments were as follows :— 
Direction of induction shock 
coil 5 cm. ( + ) Galv. -W- 
Closure. 
•003"-15" 
30"—45" 
60"—75" 
90"—105" 
Experiment 1. 
+ oo , sinking to + 500 
+ 500 
+ 98 
+ 58 
Experiment 2. 
+ oo , sinking to +400 
+ 110 
+ 62 
+ 40 
Direction of induction shock 
coil 7 cm. Galv. T v 
■003"-15" 
30"-45" 
50"-75" 
90"-105" 
( + ) Experiment 3. 
+ 510, sinking to + 260 
+ 85 
+ 52 
+ 33 
( —) Experiment 4. 
+ 225, sinking to +170 
+ 68 
+ 40 
+ 25 
The induction shock is thus followed by a prolonged electromotive change which 
subsides at first rapidly and then more slowly, thus resembling the after-effect of the 
response. It differs from this as regards its duration, as it lasts somewhat longer. 
As it can be produced by induction currents in either direction, (+) or (—), it can 
only be an excitatory change. It is always of the character which the excitatory 
changes of the organ follow, the dorsal surface of the organ becoming ( + ). It is 
remarkable that it is more effectually produced by ( + ) than by (—) induction 
currents. This does not prevent our regarding it as an excitation phenomenon, for 
the nerve itself is more readily excited by descending than by ascending currents, 
and a (+) current through the organ may play the part of a descending one for the 
majority of nerves and nerve endings which lie in its path. If it is an excitation 
phenomenon, the organ must behave like the nerve with respect to increasing strength 
of stimulus. That this is so the following experiment shows, the numbers indicating 
readings of the position of the light on the scale made at intervals of 15 ,/ after the 
maximum deflection had been reached. Strip of organ, 36 mm. long, 5 mm. wide. 
