488 STUDIES IN GENERAL PHYSIOLOGY 
mirror, but that a moistened glass plate is just as good a 
mirror as a metallic plate. If we were dealing with the 
effect of waves, this would not have been the case, as electric 
waves penetrate a thin layer of water more easily than a 
metal plate. Secondly, the body of the experimenter can be 
used in this experi- 
——_—_—__0 oO ment instead of 
a mirror. The ex- 
perimenter needs 
ay - only to bring one 
+ — [~ = hand into the 
me ° neighborhood of 
FIG, 143 
the sphere a (Fig. 
142), the other in the neighborhood of the end 6 of the 
muscle preparations. In this way the muscle can be made 
to contract, and the result might convince any believer in 
telepatHy that his superstition has a scientific foundation. 
In the latter case the effects of induction are too apparent, 
the effects of a reflection of waves too improbable, to allow 
one to think of a wave-effect. 
The last series of experiments which I published con- 
sisted in the inhibition of the electrical effects through a 
screen. The preparation lies parallel to the spark discharge 
and in a position symmetrical with reference to the spheres 
of the discharger (Fig. 138). The preparation contracted 
energetically each time the spark passed between the spheres 
of the discharger. If now a metal screen SS, (Fig. 143) 
is placed behind the preparation and parallel to it, these 
effects disappear. This can be explained as the result of 
induction. A distribution of the electricities will be induced 
in the mirror by the two spheres in the same sense as in the 
muscle preparations. Since the same kinds of electricity lie 
opposite each other in the mirror and in the nerve-muscle 
preparations, the effect upon the muscle preparations must 
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