OF THE ELECTRICAL ORGAN OF TORPEDO MARMORATA. 
521 
Tlie difference between the successive readings is given in the right-hand column, 
from which it is seen that the after-effect sinks much more rapidly during the first 5" 
than subsequently, and that with regard to this first five seconds its fall is most rapid 
in the first two seconds. 
The great prolongation of the after-effect allowed the employment of another method 
of reading, which had been used with good results in the investigation of prolonged 
polarisation after-effects. The “ falling time ” of the galvanometer needle was known 
to be fifteen seconds. The galvanometer was, therefore, closed for fifteen seconds, and 
the closure followed by a break of the circuit for the same time, this by a re-closure, 
and so on. 
The deflections obtained are strictly comparable, each being procured with the 
galvanometer needle at zero, and any instrumental error thus obviated. 
Galvanometer circuit closed 1''—15". 
„ broken 15"-30" 
„ „ closed 30"-45" 
„ ,, broken 45''-60'' 
,, ,, closed 60"-75" 
Effect + 650 
+ 130 
+ 60 
.. + 5 
+ trace, followed by —. 
The two gaps 15' -30" and &5"~6Q" were filled up by repeating the experiment, 
reversing the times of closure and of break. 
Another experiment on the same subject was suggested by the applicability of this 
method—an experiment in which the nerve should be excited mechanically. 
Such mechanical excitation had been tried with the aid of Tigerstedt’s excitor 
(32), modified for this special research, but without any good result—the low excita¬ 
bility of the nerve being a bar to the use of this method, as only feeble and uncertain 
organ responses followed excitation of this character. It had, however, been noticed 
that section of the nerve always produced a large response of the organ. The inves¬ 
tigation of the after-effect following the response evoked by section of the nerve 
was therefore quite practicable. In order to follow the change in the after-effect, the 
sensibility of the galvanometer was decreased by raising the control magnet, so that 
the falling time of the needle should be ten instead of fifteen seconds. 
With the galvanometer circuit closed, the nerve of a nerve-organ preparation from a 
large vigorous Torpedo was divided with sharp scissors 35 millims. from the organ ; a 
very large response followed the section, the deflection amounting to +750 G. yoo- 
On comparing this with the fullest response to electrical excitation which could be 
obtained in the same preparation, it was found to be of about equal amount, the latter 
giving + 670 G. T+o-. 
The galvanometer circuit was now closed and opened alternately at stated intervals 
after section of the nerve, and the prolonged after-effect thus observed ;— 
MDCCCLXXXVIT.- -E. 
3 X 
