DBA TH S T L 16HTNING. 333 



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 one-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 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 

 Las been published by Dr. Du Bois-Keyinond in the " Proceedings of 

 the Royal Institution" for 1866, vol. iv., p. 575. 



