504 
ME. F. GOTCH ON THE ELECTROMOTIVE PROPERTIES 
For this purpose I had taken with me a spring myograph, constructed on the plan 
of du Bois-Reymond, but furnished with three special keys to fit it for use as a 
rheotome. 
The passage of the traveller opened these keys in succession; they could be 
adjusted with great accuracy at any distance one from the other. The three keys 
may be distinguished as K 1? K 2 , K 3 . These were arranged so that the break of K x 
opened the primary circuit of an induction apparatus ; that of K 2 a circuit which, 
when closed, short-circuited the galvanometer ; and K 3 the galvanometer circuit itself. 
The galvanometer was the same as in the previous experiments, and was brought to a 
degree of sensibility that, with a resistance of 10,000 ohms, besides that of the instru¬ 
ment, *0001 Tt. gave a deflection of 230 scale. It was often necessary to allow only 
iVj Too; or ToVo °f the total current in the circuit to pass through the instrument. 
This was effected by the shunt provided with the instrument, and the terms G. yq, 
G. xoo) Gh ttrto> express this in all the experimental data which follow. Since the 
use of the shunt diminishes the total resistance in the circuit, a resistance of 
10,000 ohms was introduced in order to ensure the complete short-circuiting of the 
galvanometer by K 3 when the shunt was used. The whole arrangement is given in 
fig. 2. The traveller of the rheotome moved with sufficient rapidity to allow an 
accurate adjustment of the keys to within ToVo" °f each other ; the movement was 
timed by recording on the plate of the traveller the vibrations of a tuning-fork 
vibrating 100 times in a second. 
Fig. 2. 
The induction apparatus used for excitation was constructed and graduated under 
the kind direction of Professor Kronecker, of Berne. 
The first experiments were made with the view of testing the arrangements, as it 
was necessary to see how far the organ response could be investigated in this manner. 
For this purpose a small Torpedo 13 cm. X 9 cm. was selected, and, the brain having- 
been destroyed, the second, third, and fourth electrical nerves were exposed and freed 
