hment. So that, besides the interval of transmission, a
still further time is necessary for the brain to put itself in
order--for its molecules to take up the motions or positions necessary
to the completion of consciousness. Helmholtz considers that
one-tenth of a second is demanded for this purpose. Thus, in the case
of the whale above supposed, we have first half a second consumed in
the transmission of the intelligence through the sensor nerves to the
head, one-tenth of a second consumed by the brain in completing the
arrangements necessary to consciousness, and, if the velocity of
transmission through the motor be the same as that through the sensor
nerves, half a second in sending a command to the tail to defend
itself. Thus one second and a tenth would elapse before an impression
made upon its caudal nerves could be responded to by a whale forty
feet long.

Now, it is quite conceivable that an injury might be inflicted so
rapidly that within the time required by the brain to complete the
arrangements necessary to consciousness, its power of arrangement
might be destroyed. In such a case, though the injury might be of a
nature to cause death, this would occur without pain, Death in this
case would be simply the sudden negation of life, without any
intervention of consciousness whatever.

The time required for a rifle-bullet to pass clean through a man's
head may be roughly estimated at a thousandth of a second. Here,
therefore, we should have no room for sensation, and death would be
painless. But there are other actions which far transcend in rapidity
that of the rifle-bullet. A flash of lightning cleaves a cloud,
appearing and disappearing in less than a hundred-thousandth of a
second, and the velocity of electricity is such as would carry it in a
single second over a distance almost equal to that which separates the
earth and moon. It is well known that a luminous impression once made
upon the retina endures for about one-sixth of a second, and that this
is the reason why we see a continuous band of light when a glowing
coal is caused to pass rapidly through the air. A body illuminated by
an instantaneous flash continues to be seen for the sixth of a second
after the flash has become extinct; and if the body thus illuminated
be in motion, it appears at rest at the place where the flash falls
upon it. When a colour-top with differently-coloured sectors is
caused to spin rapidly the colours blend tog