1887.] Mr G. N. Stewart on the Polarisation of Nerve. 205 
6. On the Effect produced on the Polarisation of Nerve by 
Stimulation. By Mr G. N. Stewart. 
In this short paper I wish merely to give a summary of the chief 
results of experiments made by me in February and March last in 
the Physiological Institute of Berlin. Du Bois Beymond has 
recently made an elaborate investigation of the galvanic polarisation 
of muscle. Many years ago he made similar observations on nerve. 
The question which occurred to me was, How does tetanus affect the 
amount of polarisation in nerve 1 Apparently there has been no 
previous work at this subject. It is not necessary to describe here 
the arrangements used, nor the manner of making the observations, 
as a detailed account, with discussion of the facts brought out, will 
appear in the Journal of Physiology. When a current is passed 
through a living nerve, the polarisation produced may be either 
negative or positive. When it is negative, the polarisation current 
is, of course, in the opposite direction to the polarising current. 
Positive polarisation gives a current in the same direction as the 
polarising stream. It depends upon the “ density ” of the polarising 
current, and upon the time of flow, whether the deflection due to 
the polarisation is purely negative, purely positive, or of double 
sign. When it is of double sign, there is first a negative kick, 
which is followed by a more persistent positive deflection. As a 
matter of fact, there is every ground for believing, that in general 
the two polarisations exist side by side in the polarised nerve. 
The influence of stimulation on the polarisation, so far as my 
experiments go, may be stated thus : — 
1. In every case the effect 'produced by stimulation is in the 
direction of diminution of the positive polarisation . — One says “ in 
the direction of,” because increase of negative polarisation would 
equally well explain the result. It is probable, however, for reasons 
which need not be given here that it is the positive polarisation 
which is affected. 
2. The effect is, ivithin limits, greater the longer the time of flow of 
the polarising stream . — This has only been shown for weak currents, 
because strong currents depress the vitality of the nerve when they 
are allowed to flow for any length of time. If, in the case of a weak 
