i 4 MOTIONS OF SECT. III. 4. 3 . 



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

 were originally excited by the ftimulus of external objels : 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 muft 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 Sedlion 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 diftinftly, 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 feems to be nothing more than the reiterated 

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

 fected. 



Other ideas that are excited by imagination or recollection 

 in many inftances produce fimilar effects on the conftitiition, as 

 our perceptions had formerly produced, and are therefore un- 

 doubtedly a repetition of the fame motions. A flory which the 

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

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

 exploded with prodigious flench ; and fome years afterwards, 

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

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

 before experienced from the perception of it. 



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

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

 as well as the power of perception. Of this a fatisfadtory in- 

 fiance has fallen under my obfervation. 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 reprefent letters. I 

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

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

 diftinct articulation, though his relations could fometimes un- 

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

 fured me, that in his dreams he always imagined that people 

 converfed with him by figns or writing, and never that he 

 heard any one fpeak to him. From hence it appears, that with 



the 



