--_Chronica Cientifica._
[Illustration: FIG. 2.]
* * * * *
APPARATUS FOR DETERMINING MECHANICALLY THE REACTION PERIOD OF
HEARING.
The following apparatus, constructed after the designs of Dr. Loeb,
assistant in the Physiological Institute at Wurzburg, is for the
purpose of measuring the reaction period of hearing, that is, the
period which elapses between the time when a sound wave affects the
auditory nerve and is thence transferred to the brain, then affecting
the consciousness, and the moment when the motor nerves can be thrown
into action by the will. It is, therefore, necessary to fix both
instants--when the sound is produced and when the observer has, from
its warning, received the impulse so as to press down a key. The great
advantage of this instrument over others adapted for the same end
consists in this, that the determination in its essentials is effected
entirely by mechanism, and, therefore, the graphic results attained by
it are free from all sources of error, which errors other methods
always introduce to a greater or less extent.
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