(Pohl'sche Wippe)
Description: The movable arm can connect three pairs of
connectors, apparently when moved by the experimenter's hand.
This device provides rapid manual switching. The switching is
accomplished by two features of this device. First, the
alternating electrical continuity is created by diagonal
connectors crossing, but not touching on the surface of the
switch. Good connection is provided by the points of the switch,
which make contact through small mercury cups. This particular
device was used in experiments like the Fritsch and Hitzig
experiment of 1870 which demonstrated that electrical stimulation
of localized brain regions could produce specific movements. This
type of switch was needed, since sources of electrical current
were not generally available from external (i.e., generator-
based) current sources. The Fritsch and Hitzig experiments
sometimes used current from batteries and sometimes from
capacitative sources like Leyden jars, and this device enabled
rapid switching of these two sources. (Expanded caption Copyright
1998, Edward J. Haupt)
(Source: None given.)
Source of illustration: Zimmermann, E. (1903). XVIII. Preis-
Liste über psychologische und physiologische Apparate
(p. 36). Leipzig: Eduard Zimmermann.
DESCRIPTORS:
Type: component, switching
Stimulus: N/A
System: N/A
Output: N/A