Bauhaus-Universität Weimar

Handbook for the Physiological Laboratory. Text
Burdon-Sanderson, John Scott E. Klein Michael Foster T. Lauder Brunton
is a figure of a tuning-fork arranged by König for recording its 
vibrations on a revolving surface. A massive stand bears the fork 
A firmly secured in it. The two coils cc (which by means of the 
arrangement k can be slid up and down the stand, so as to 
accommodate themselves to tuning-forks of different lengths) 
project over the two ends of the fork, and each bears a screw d 
which can be screwed as desired up to or away from the ends of 
the fork. The upper arm of the fork bears at its end a rod a 
with platinum point which dips into the mercury cup b. 
The tuning-fork B, which must have the same rate of vibration 
as A, is fixed into a light moveable stand, so that it can be placed 
in such a position that the light elastic marker g may touch with 
the least excess of friction the recording surface. This fork is 
placed in the same manner as A, with its ends between the coils 
ed, bearing similarly the screws ff'. 
One wire from a battery w is connected wdth a binding screw 
at the handle of the tuning-fork A, and is thus in electric con¬ 
tinuity with the rod a. The mercury cup b is connected by a 
wire z with the coil e of the fork B. The other pole of the 
battery is connected by x with the coils c d of A, and thence by 
y with the coil d of B. 
The screws d d, f // being brought rather near to their re¬ 
spective forks, place a small quantity of mercury covered by a little 
spirit in the cup b, and having set the fork A vibrating a little, 
screw the rod a up or down until magnetic interruption is fairly 
established. B will then be found vibrating synchronously with 
A, and the point g will be found tracing curves on the recording 
surface, the interval of time corresponding to each curve being i 
determined by the pitch of the fork. Screw the d d, /// as far ] 
away from their respective forks as can be done without stopping l 
the current altogether. 
XIII. Arrangement of Electrical Apparatus.—Constant 
Current.— Place the nerve (or muscle, when muscle alone is the 1 
subject of experiment) on the electrodes, taking care that the 
nerve is actually in contact with each electrode. When the non- 
polarizable electrodes are used, their plugs must be kept damp 
with the normal saline solution : avoid making tnem too wet, 
and especially do not let a bridge of fluid form along the nerve 
between the two electrodes. 
Bring the wire from each electrode to the outer binding screw on 
each side of a Du Bois Reymond^s key (fig. 300). Bring the wires 
from the battery to the inner screws of the same key. Let the 
positive wire, the wire connected with the copper, carbon, platinum, 
&c., of the battery be coloured of some definite colour, e.g.} red ; 
let the wire fastened to the same side of the key have the same 
colour. The electrode connected with this wire will be the


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