238 Proceedings of Royal Society of Edinburgh. [sess. 
which was at first used ; a , b, c , d , represent the lengths of nerve 
IA, AB, BC, and CD, respectively. 
Experiments 1 and 2 are examples of the first method with- 
out compensation; Experiments 3 and 4, with compensation. 
It will be seen that on the cathodic side, i.e ., with ascending 
current, the stimulation effect has the negative sign with reference 
to the direction of the polarising stream. On the side of the 
anode the same is true up to an electromotive force of about 3 
Daniells working through 9 mm. of nerve. Above this the effect 
becomes positive. This is so only when the distance C is small. 
In Experiment 4 it is seen that, with C = 6J mm., the positive 
effect does not appear with 7 Daniells, nor even when C -3J mm. 
When C is reduced to 1 mm., it comes in even with 3 Daniells. 
Experiment 1. 
Distances — a, 9 mm. ; b, 10 mm. ; c, 2 mm. ; d, 9 mm. 
I Polarising Current. 
Stimulation 
Effect. 
Polarising Current. 
Stimulation 
Effect. 
1 D Rh. 100 cm. * 
1 D i 
-12 
4 
- 3 
1 D 4 
-15 
4 
- 3 
3 D t 
-55 
1 D Rh. 2000 cm. 4 
-25 
3 D 4 
+ 50 
t 
-20 
5 D t 
-42 
1 D 4 
-20 
5 D 4 
+ 53 
Experiment 2. 
Polarising Current. 
Stimulation 
Effect. 
lDf 
-14 
Galv. shunt 10. 
1 D 4 
-16 
3 D 4 
+ 45 
4 D 4 
+ 29 
No compensation in Experiments 1 and 2. 
Experiment 3. — Here two sets of observations were taken on 
the same nerve, the distance between electrodes B and C being 
altered. 
* The total resistance of the Rheochord was 2000 centimetre units. 
