OF THE ELECTRICAL ORGAN OP TORPEDO MARMORATA. 
519 
of one from a medium-sized vigorous fish. The curves c and d are short curves 
representing the change in the organ of a large Torpedo, c being that of the organ 
at 20° C., and d that of the organ at 5° C. In the curve a the ordinates represent 
the readings of the galvanometer with the y-jjo shunt, and the curve corresponds in 
duration to the duration of the effect as ascertained by Marey. 
In reality, however, the effect is prolonged far beyond seven hundredths of a 
second. This prolongation was apparently not capable of affecting Marey’s “ physio¬ 
logical” galvanoscope, viz., the muscle-nerve preparation; its existence is, however, 
easily ascertained by the galvanometric method when the galvanometer is used 
without the shunt, and, owing to its slow subsidence, it produces well-marked 
galvanometric deflections. The large response has a long tail, if the expression may 
be used. It is termed here the “after-effect ” of the response. 
The after-effect of the response— The fast-moving rheotome previously used was not 
adapted to the examination of the after-effect, since the range of the instrument did 
not extend beyond •08". The rheotome was therefore now used for giving an induc¬ 
tion shock of constant intensity and duration for purposes of excitation, and the key 
Ko was placed so as to be broken '06" after the exciting key K x . For K 3 there was 
substituted a key which could be closed quickly by the hand, this closure being 
•effected at various intervals after the release of the traveller of the rheotome. 
Successive experiments were now made, first with the galvanometer circuit closed, but 
short-circuited by K 3 ; the deflection obtained thus indicated the effect which followed 
the excitation from ’06" onwards. The galvanometer circuit was then closed 1" after 
the release of the rheotome, and the resulting deflection observed. The difference 
between the two readings was a measure of the amount of the slowly subsiding change 
during the period ’06" to 1". The same plan was adopted with a closure 2", 3", 4", 
&c., after excitation. 
As the after-effect following a response is a new feature of the excitatory change, it 
will be advisable to describe an experiment with some detail. 
A block of organ was cut from a large vigorous Torpedo ; the block measured 
53 millims. in the direction of the columns, and was 35 millims. in width and 
30 millims. in thickness. Its cut surface showed four injured columns, and, conse¬ 
quently, it contained twelve uninjured columns, all supplied by branches of the second 
electrical nerve. This was excited 20 millims. from its point of entry into the organ 
by the break of 2 Groves in the primary circuit of the induction apparatus at intervals 
of three minutes. The organ-current obtained by leading off the skin-covered ends of 
the columns amounted to -f "0125 R. It subsided rapidly, and then slowly, but sank 
after each excitation, and was compensated. This fall is given in terms of the 
galvanometer scale, it having been ascertained that a deflection of 130 scale corre¬ 
sponded to a difference of potential = - 0003 R. The fall is, of course, opposed to the 
after-effect. The galvanometer was used without its shunt. 
