VOLUNTARY MOTION. 495 



lacerated or pricked by a pin or nail on any part of the face or 

 rest of the surface, it was still motionless, and gave no evidence 

 of impression. But on touching the eyelash with a straw, the eye 

 forcibly closed ; on touching the cornea, the eye rolled outwards ; 

 and on touching the verge of the anus, the sphincter contracted, 

 the tail was raised, and the vulva drawn towards the anus. Now 

 this only shows what is well known, that tickling certain ex- 

 quisitely sensible parts with a straw induces a stronger im- 

 pression than rough usage with a nail or pin. A person who 

 could bear pain without flinching, could not remain still under 

 tickling of certain parts : and yet it is only certain parts that are 

 so ticklish. The sensible ends of the fingers or the back of the 

 hand may be touched with a straw in vain. Dr. M. Hall himself 

 shows that a strong impression made any where would equally 

 excite motion. For he goes on to repeat the very experiment of Sir 

 Gilbert Blane. He divided the spinal chord of a frog below the occi- 

 put. The animal was still. He pinched, not tickled, a toe with a pair 

 of forceps. Both hind extremities moved. He pinched again, 

 and the motions recurred. Now this was not an eyelash, the 

 cornea, or verge of the anus, but some other part of the surface, 

 and it might of course have been any sensible part, and the cor" 

 responding muscles of the part would have acted. If a corre- 

 spondently strong impression had been made in the horse, mo- 

 tion-would have equally taken place. Surely, when we wink 

 on the eyelash being touched, we do this by precisely the same 

 operation as when we withdraw a hand that is struck. Of course, 

 when the spinal chord is destroyed, or any portion of the ence- 

 phalon is destroyed in which are the extremities of the nerves of 

 sensation that convey the impression, or the extremities of the 

 nerves of motion that convey the stimulus to the muscles, or in 

 which they meet, as they probably do, no effect from pricking or 

 tickling, &c. can ensue. Dr. M. Hal! considers that the excitor 

 nerves of the excito-motory system are the ganglionic portion 

 of the fifth and of each spinal nerve, and the pneumono-gastric ; 

 the motor nerves of it, the aganglionic portion of the fifth and of 

 each of the spinal nerves ; the fourth, sixth, seventh, and ninth 

 encephalic, the pneumono-gastric and its pharyngeal and laryn- 

 geal branches, the spinal accessory, the phrenic, and Sir C. Bell's 

 external respiratory. 



Now really the whole truth appears to be what is well known, 



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