534 
MR. F. GOTCH ON THE ELECTROMOTIVE PROPERTIES 
This shows that two nerve-organ responses are summed even when produced '005" 
after one another. It is, therefore, to be expected that the after-effects should also 
be summed, and experiments were now made as to summation of the after-effect of a 
nerve-organ response and that produced by the passage of an induction current. In 
order to obtain this result, it was necessary to lead an induction shock through the 
organ at a short interval of tune after the organ response had been evoked by excita¬ 
tion of its nerve. For this purpose the rheotome was so arranged that K 2 should 
break the primary circuit of one induction apparatus and thus excite the nerve, whilst 
after an interval of '02" Ko broke the primary circuit of an induction apparatus 
arranged so as to allow the break-shock to traverse the organ. Finally, K 3 was 
arranged so as to short-circuit the galvanometer up to '05". The deflections obtained 
thus showed either the after-effect of the nerve-organ response only, or that following 
the passage of the induction shock only, or the summation of the two after-effects. 
A nerve-organ preparation was made by carefully dissecting out a long piece of the 
second nerve, and then cutting out a thin strip which should contain columns supplied 
by it. It was then necessary to ascertain that the preparation gave a large nerve- 
organ response followed by a prolonged after-effect. With K L at 0", K 3 at '02", and 
K 3 at '05", the results were as follows :— 
After-effect. 
Break of and K g — 
After-effect following nerve-organ response 
Break of K 3 and K 3 — 
After-effect following passage of induction, 
current only. 
Break of K l5 K 3 , and T\ ;S — 
Summation of two effects 
15" 
.+ 
220 
30" 
.+ 
100 
■{ 45" 
.+ 
50 > 
60" 
.+ 
35 
75" 
.+ 
18 J 
f 15" 
.+ 
240 q 
30" 
.+ 
no ! 
< 45" 
.+ 
40 J. 
| 60" 
.+ 
25 1 
L 75" 
.+ 
5 1 
f 15" 
.+ 
500 q 
cc 
o 
.+ 
250 1 
I 45" 
.+ 
100 ^ 
f60" 
.+ 
50 
The experiment shows with the greatest distinctness the striking resemblance 
between the electromotive change following the nerve-organ response and that 
following the passage of the induction current. It shows how completely the summa¬ 
tion of the two after-effects is effected, and hence is decisive as to the efficacy of the 
induction current for the production of the after-effect, whether the organ be in a 
state of quiescence or in that state of activity into which it is thrown by stimulation 
of its nerve. There is thus no escape from the conclusion that, as the passage of an 
induction shock through a strip of organ is followed by a prolonged excitatory change, 
the passage of the current produced by the nerve-organ response itself must, if equal 
in intensity to the induction shock, be followed by a similar prolonged excitatory 
change. 
o 
