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PEOPLE in general imagine, When they think at all about
the matter, that an impression upon the nerves—a blow,
for example, or the prick of a pin—is felt at the moment it
is inflicted. But this is not the case. The seat of sensa-
tion is the brain, and to it the intelligence of any impression
made upon the nerves has to be transmitted before this
impression can become manifest in consciousness. The
transmission, moreover, requires time, and the consequence
is, that a wound inflicted on a portion of the body distant
from the brain is more tardin appreciated than one inflicted
adjacent to the brain. By an extremely ingenious experi-
mental arrangement, Helmholtz has determined the velocity
of this nervous transmission, and finds it to be about one
hundred feet a second, or less than one-tenth of the velocity
of sound in air. If, therefore, a whale fifty feet long were
wounded in the tail, it would not be conscious of the injury
till half a second after the wound had been inflicted.l But
this is not the only ingredient in the delay. There can
scarcely be a doubt that to every act of consciousness be-
longs a determinate molecular arrangement of the brain-—
that every thought or feeling has its physical correlative in
that organ; and nothing can be more certain than that
every physical change, whether molecular or mechanical,
requires time for its accomplishment. So that, besides the

1 A most admirable lecture on the velocity of nervous transmission

has been published by Dr. Du Bois-Raymond in the Proceedings of the
Royal Institution for 1866, vol. iv. p. 57 5.

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