APPENDIX I. 99 



injured state of the nerve, being checked by so gross 

 an obstacle as a cut or a ligature, it must necessarily 

 be something material, not, however, the electricity 

 such as it moves along a telegraph-wire, for this 

 would readily overleap those impediments* But, 

 whatever the nervous agent may be, it obviously 

 must proceed in the nerves with a certain definite 

 velocity. In other words, however great this ve- 

 locity may be, a certain definite time will be required 

 for the messages of the brain to reach the muscles 

 and for those of the senses to reach the brain. 



In common life, it is true, we never notice any 

 phenomenon indicative of such a delay in the trans- 

 mission of despatches in our nerves. Certainly our 

 limbs do not instantaneously carry out the orders of 

 our will ; but this is rather owing to the circum- 

 stance of time being required for motion. On the 

 other hand, we fancy we see the light, we hear the 

 sound, we feel the prick on the toes as well as on 

 the cheek at the very instant the corresponding 

 organs of the senses have been affected. But a 

 little reflection shows that this is altogether a 

 delusion; in fact, if we only had one sense, an 

 indefinite time might elapse between its organ being 

 affected and the sensation taking place in the brain, 

 without our perceiving it ; we simply should always 

 be so much behind the real time, just as we are 

 when listening to distant music, or when looking at 

 the stars. The same thing would also happen if we 

 had two senses, both equally slow in working. We 

 should only perceive that something was wrong, if 

 the two senses had a different rate of working, and 



