14 MOTIONS OF Sect. III. 4 . 3, 



than a reiteration of thofe motions of the organs of fenfe, which 

 were originally excited by the itimulus of external objects : and 

 in our waking hours the fimple ideas, that we call up by recol- 

 lection or by imagination, as the colour of red, or the fmell of 

 a rofe, are exact refemblances of the fame fimple ideas from 

 perception ; and in confequence mull be a repetition of thofe 

 very motions. 



3. The difagreeable fenfation called the tooth-edge is origin- 

 ally excited by the painful jarring of the teeth in biting the edge 

 of the glafs, or porcelain cup, in which our food was given us 

 in our infancy, as is further explained in the Section XVI, 10, 

 on Inftinct.— This difagreeable fenfation is afterwards excited 

 not only by a repetition of the found, that was then produced, 

 but by imagination alone, as I have myfelf frequently experien- 

 ced ; in this cafe the idea of biting a china cup, when I imagine 

 it very diftinctly, or when I fee another perfon bite a cup or 

 glafs, excites an actual pain in the nerves of my teeth. So that 

 this idea and pain feem to be nothing more than the reiterated 

 motions of thofe nerves, that were formerly fo difagreeably af- 

 fected. 



Other ideas that are excited by imagination or recollection 

 in many inftances produce fimilar effects on the conititution, as 

 our perceptions had formerly produced, and are therefore un- 

 doubtedly a repetition of the fame motions. A (lory which the 

 celebrated Baron Van Swieten relates of himfelf is to this pur- 

 pofe. He was prcfent when the putrid carcafs of a dead dog 

 exploded with prodigious ftench ; and fome years afterwards, 

 accidentally riding along the fame road, he was thrown into the 

 fame ficknefs and vomiting by the idea of the ftench, as he had 

 before experienced from the perception of it. 



4. Where the organ of fenfe is totally deftroyed, the ideas 

 which were received by that organ feem to perifh along with it, 

 "3 well as the power of perception. Of this a fatisfactory in- 

 ftance has fallen under my observation. A gentleman about 

 fixty years of age had been totally deaf for near thirty years : 

 he appeared to be a man of good underftanding, and amufed 

 himfelf with reading, and by converfing either by the ufe of the 

 pen, or by figns made with his fingers, to represent letters. I 



1 that he had fo far forgot the pronunciation of the lan- 



^ that when he attempted to fpeak, none of his words had 



ct articulation, though his relations could fometimes un- 



dcrfland his meaning. But, which is much to the point, he af- 



fured mc, that in his drenms he always imagined that people 



converfed wii n by figns or writing, and never that he 



>ne fpeak to hii From hence it appears, that with 



the 



