512 
MR. F. GOTCH ON THE ELECTROMOTIVE PROPERTIES 
(2.) Effect of strength of stimulus .—In all the preceding experiments a stimulus 
had always been used of such strength as to procure a large response of the organ. 
The importance of procuring a maximal contraction in the investigation of similar 
phenomena in muscle is -well known, but in endeavouring to obtain a maximal 
response of the electric organ to stimulation of its nerve we are confronted with a 
difficulty which is not present in the case of muscle. The range of stimuli which call 
forth minimal effects in the latter is very limited; in the nerve-organ preparation, on 
the other hand, it is large. The organ is a better interpreter than the muscle of the 
change produced in a nerve by the passage of an induction current. A far stronger 
stimulus is necessary to excite the nerve-organ than the nerve-muscle preparation ; 
but, once this strength has been reached, the nerve-organ preparation responds more 
and more fully, the stronger the stimulus, until, with a damaging strength of current, 
the nerve itself is injured. The following experiment is selected from several to 
illustrate this. 
A nerve - organ preparation was made from the organ of a large Torpedo, 
42 cm. X 29 cm. The nerve was excited by the break of K 1? and K 2 was so placed 
as to be broken ■005" later ; the third key, K s , was not used. The point of excitation 
was 20 millims. from the organ. 
Primary circuit with 2 Groves. 
Coil with core. 
Effect. 
Secondary coil, 
20 
centims. 
(150) . . . 
G. T n 
0 
11 
17 
11 
(300) . . . 
G. X V 
+ 30 
11 
16 
11 
(400) . . . 
G- To 
+ 700 
11 
15 
11 
(700) . . . 
G. Jg- 
+ qo 
11 
17 
11 
(300). . . 
G. T V 
+ 15 
l 1 
16-5 
11 
(350). . . 
G. Yo* 
+ 45 
5? 
16 
11 
(400) . . . 
G. T V 
+ 650 
11 
15 
11 
(700). . . 
G -m 
• lOO 
+ 110 
11 
12-5 
11 
(2000) . . 
G -±- 
^ * lOO 
+ GO 
11 
12'5 
11 
(2000) . . 
G 1 
^ ’ lOOO 
+ 90 
(The numbers in brackets denote the relative strengths of the induction shocks.) 
After an interval the strength of stimulus was still further increased. 
Primary circuit with 2 Groves. 
Coil with core. 
Effect. 
Secondary coil, 12‘5 centims. (2000) 
G - J — 
^ • lOO 
+ 365 
10 „ (4500) . . 
G 
^ • lOO 
+ 670 
„ 7-5 „ (7000) . . 
lOO 
+ 620 
With the secondary coil varied from 17 to 10 centims.—that is to say, with relative 
strengths of shock from 300 to 4500—the organ response became fuller, the stronger 
the stimulus. In the case of a large Torpedo the nerve bundles are of great 
thickness ; the second nerve in the above experiment measured 5 millims. in diameter. 
