EXCURSIONS OF THE CAPILLARY ELECTROMETER. 
97 
and the value of each excursion, as measured by its subnormal, may be compared with 
that obtained by calculation. 
No. 290.—Rider of the rbeocbord set at 67 centims. Muscle-current = 42 Jcentims., giving an 
effective difference of potential of 25 centims. Subnormal at tbe commencement of the excursion 
= 8'19 centims. Calculated 
83 : 25 :: 26'945 : 8T2. 
No. 292.—The difference of potential was simply that due to the muscle-current, which had fallen to 
37 centims. The excursion was therefore in tbe opposite direction. Subnormal at tbe commencement 
of tbe excursion = 11'955 centims. Calculated 
83 : 37 :: 26'945 : 12-01. 
These results agree fairly well. For greater accuracy, the actual measurement of 
the subnormal was made in all cases at a point from 2 millims. to 5 millims. from the 
commencement, and the difference of the ordinates of the measured point and of the 
zero line, multiplied by the constant factor 8 "5, added to the result. Hence the 
number of places of decimals. (See Part II., p. 101.) 
The muscle was then removed from the circuit, and the following experiments made. 
No. 294.—Upward excursion (towards tbe tip of tbe capillary) given by 80 centims. of tbe rbeocbord 
wire. No external resistance. Subnormal at tbe commencement of tbe curve = 28'2 centims. 
No. 295.—Upward excursion given by 80 centims. of tbe rbeocbord wire. External resistance 
= 1000 ohms. Subnormal at the commencement of the curve = 28'04 centims. 
No. 296. Downward excursion given by 80 centims. of tbe rbeocbord wire. External resistance 
= 1000 obms. Subnormal at tbe commencement of tbe curve = 28'14 centims. 
These results show the identical character of the upward and downward excursions, 
and also that the introduction into the circuit of 1000 ohms makes no very marked 
difference ; they do. however, indicate the effect of taking away the resistance of the 
muscle and its electrodes, in that the value of the constant multiplier has risen from 
8'5 to about 9'2. 
Artificial Spikes. 
This name was given to the curves obtained by photographing the excursions 
produced by means of two currents in opposite directions, each lasting about ’005 sec. 
It was intended to imitate as nearly as possible the effect produced by the excitation 
of muscle, with differences of potential of known value and duration, so as to 
determine whether the capillary electrometer was capable of distinguishing between a 
current of definite strength suddenly thrown into it, and a more or less gradual rise 
of a difference of potential, extending over a period of equal duration. That it can 
do so was shown beyond a doubt. To produce these artificial spikes, the wires from 
the electrometer were joined up through the derived circuits of two rheochords, 
A and B, each of which was provided with a separate battery. These were connected 
MDCCCXCII.—A. o 
