BRAIN AND NERVOUS SYSTEM. 337 



were any cause of suffering pressing upon it, while others 

 have laughed at the fallacious imagination. A gentleman, 

 whose arm was recently amputated by a surgeon on account 

 of a cancer in the hand, said that when the end of the nerve 

 was touched in the stump, he felt his old pain in the hand. 

 In these and similar cases, there was no mistake in the sensa- 

 tion; the remaining trunk of the nerve, being pressed or 

 irritated, carried this impression to the brain, which referred 

 the pain to the separated limb, and to no other. This has 

 sometimes happened many years after amputation. The 

 reasoning faculty corrects the error, yet the sensation remains. 



772. The same law holds in regard to the nerves of mo- 

 tion. The muscles yield obedience to the mandates which 

 they receive from the brain. When the mind wills to move 

 the finger, the brain sends the volition and the stimulus of 

 contraction along the motory nerves to the muscles on the 

 fore-arm, and they contract and bend the finger. But the 

 muscles yield to every stimulus they receive through the 

 motory nerve. If, therefore, we prick or irritate one of the 

 nerves of motion, the muscles to which it leads will contract; 

 if we apply a galvanic shock to it, it will produce the same 

 effect ; and even the limbs of the dead body, for a short 

 time after death, can be made to move by the powerful appli- 

 cation of galvanism to the nerve of motion. 



773. False sensations are produced directly in the brain, 

 independent of the nerve, by some disease which disturbs, 

 or excites, or impresses the brain, at the points where the 

 nerves terminate. When this impression is received in the 

 brain, from the outer end of the nerve, a true sensation is 

 excited ; but when it is made directly upon the brain, by dis- 

 ease or disturbance, without the intervention of the nerve, a 

 false sensation is the consequence. 



The communicating-bells in the hotel ( 770, p. 336) may 

 be rung by any jar, or any thing moving them, independent 

 of the wires that should pull them ; then the servant would 

 have the usual idea of some one ringing at the farther end 

 of the wire, and something wanting in the chamber where 

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