DEA TH BY LIGHTNING. 3 33 
before this impression can become manifest as conscious- 
ness. 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 tardily appreciated 
than one inflicted adjacent to the brain. By an extremely 
ingenious experimental arrangement, Helmholtz has deter- 
mined the velocity of this nervous transmission, and finds 
it to be about eighty feet a second, or less than oue-thir- 
teen-th of the velocity of sound in air. If, therefore, a 
whale forty 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.* But this is not the only in- 
gredient in the delay. There can scarcely be a doubt that 
to every act of consciousness belongs a determinate molec- 
ular 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 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 con- 
sciousness. Helmholtz considers that one-tenth of asecond 
is demanded for this purpose. Thus, in the case of the 
whale above supposed, we have first half a second con- 
sumed in the transmission of the intelligence through the 
sensor nerves to the head, one-tenth of asecond 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 t the time required by the 
brain to complete the arrangements necessary to conscious- 
ness, its power of arrangement might be destroyed. In such 
a case, though the injury might be of a nature to cause 
* A most admirable lecture on the velocity of nervous transmission 
has been published by Dr. Du Bois-Reyinond in the " Proceedings of 
the Koyal Institution" for 1866, yol, iv., p. 575, 
