APPENDIX I. 121 



metres (97'1 feet) in one second, which is only very 

 little more than the result obtained for the motor 

 nerves of the frog. (See pages 109 and 112.)* 



By similar experiments, Dr. Schelske has ascer- 

 tained that the transmission of sensation through the 

 spinal cord of man takes place at very nearly the 

 same rate as in the nerves. This is the more 

 remarkable, as in other respects the nerve-tubes 

 undergo a material change on entering the spinal 

 cord, where, according to Professor van Been, of 

 Groningen, and others, they are no longer capable 

 of stimulation by electricity, chemical substances, 

 mechanical injuries, &c. 



Considerations suggested by the foregoing Results. 

 The following table affords an opportunity of 

 comparing the velocity of the nervous agent, as it 

 has been established by the foregoing researches, 

 with that of several other agents, or bodies in 

 motion, from which comparison some interesting 

 conclusions may be drawn : 



VELOCITY OF Metres in one second. 

 Electricity in Mr. Wheatstone's ex- 

 periment .... 464,000,000 



Light 300,000,000 



Sound in Iron .... 3,485 



Water .... 1,435 



Air .... 332 



Shooting Star .... 64,380 



Earth in Orbit round Sun . . 30,800 



Earth's Surface at Equator . . 465 



* Reichert's und du Bois-Reymond's Archiv, u. s. w., 1864, 

 S. 151. 



