EXCURSIONS OF THE CAPILLARY ELECTROMETER. 
103 
of the subnormal—reducing it subsequently to decimals of a volt. The total indi¬ 
cated difference of potential will therefore be 
± cy dz cl. 
Attention must be paid to the sign of both y and l. In the examples given, an 
upward excursion is produced by the negative variation, so that the formula for the 
first phase will be 
— cy — 8’5 1. 
At the apex the subnormal passes through zero, but the total indicated potential is 
not yet zero, being indicated truly by the distance of the meniscus from the zero line, 
i.e., the actual height of the excursion. This, expressed on the same scale as before, is 
- 8-5 1. 
During the second phase, or descending portion of the curve, the subnormal is 
positive, and we must write 
-f- cy — 8'o/. 
If, as sometimes happens, the meniscus should descend below the zero line, l also 
becomes positive, and we have 
T* cy -)- 8 'oh 
It is unnecessary to describe minutely the arrangement of the physiological prepara¬ 
tions. The photographic curves of which the analysis is given are some of those 
obtained in the experiments in which I assisted Professor Burdon Sanderson, to 
whose kindness I am indebted for permission to make use of them in this, the first 
application of the method of analysis which this paper describes. 
Non-polarizable electrodes were employed, one ( f ) placed on the tendon, and the 
other (m) on the belly of the muscle, unless otherwise stated. The muscle was kept 
stretched by a weight, not greater than could be lifted by a moderate contraction. 
The exciting electrodes were applied to the nerve, the exact instant of the stimulus 
being marked by the upward movement of the arm of the signal-key, the shadow of 
which is recorded on the plate. This key, which has been already referred to, was 
placed in the primary circuit of the induction-coil, and by its use, all possibility of 
delay in registering the instant of the induction shock was eliminated, save that due 
to the induction coil itself. 
No. 287. Fig. 11, a, Plate 4.—Gastrocnemius of U. esculenta. Exciting electrodes placed at tlie 
extreme end of tlie prepared nerve, as far as possible from the muscle. 
The muscle current was balanced by the difference of potential derived from 42 centims. of the wire of 
the rheochord. The analysis of this curve is given in fig. 11. The excursion is not large, but the 
negative variation is sudden, and remains tolerably constant for some time. The positive variation is 
not great, but the return to the original zero is slow. 
The relative value of the muscle current is shown by the dotted line, which represents the true zero 
potential. 
