1^8 Mr, Bell on the nervous circle which connects 



not a conductor towards the brain, and that it cannot perform 

 the office of a sensitive nerve. 



Without attempting to determine the cause, whether de- 

 pending on the structure of the nervous cord, or the nature, 

 or the source of the fluid contained, a pure or simple nerve 

 has the influence propagated along it in one direction only, 

 and not backwards and forwards ; it has no reflected opera- 

 tion or power retrograde ; it does not both act from and to 

 the sensorium. 



Indeed reason without experience would lead us to con- 

 clude, that whatever may be the state, or the nature of the 

 activity of a motor nerve during exertion, it supposes an 

 energy proceeding from the brain towards the muscles, and 

 precludes the activity of the same nerve in the opposite 

 direction at the same moment. It does not seem possible 

 therefore that a motor nerve can be the means of communi- 

 cating the condition of the muscles to the brain. 



Expose the two nerves of a muscle ; irritate one of them, 

 and the muscle will act ; irritate the other, and the muscle 

 remains at rest. Cut across the nerve which had the power 

 of exciting the musclfe, and stimulate the one which is undi- 

 vided — the animal will give indication of pain ; but although 

 the nerve be injured so as to cause universal agitation, the 

 muscle with which it is directly connected does not move. 

 Both nerves being cut across, we shall still find that by 

 exciting one nerve the muscle is made to act, even days after 

 the nerve has been divided; but the other nerve has no 

 influence at all. 



Anatomy forbids us to hope that the experiment will be 



