Si CT. XVIII. 18. 19. O F S L E E P. 255 



is fufpended, and all external famuli are excluded 

 in fleep, this flight er connexion of ideas take place ; 

 and the train is laid to be inconfiflent ; that is, difli- 

 inilar to the ufual order of nature. 



But, when any con lift en t train of fenfitive or vo- 

 luntary ideas is flowing along, if any external ftimu- 

 lus affects us Ib violently, as to intrude irritative 

 ideas forcibly into th-e mind, it difunites the former 

 train of ideas/, and we are affected with furprife* 

 Thefe ftimuli of unufual energy or novelty not only 

 difunite our common trains of ideas, but the trains of 

 tnufcular motions alfo, which have not been long 

 eflablifhed by habit, and diftarb thofe that have. 

 Some people become motionlefs by great furprife, 

 the fits of hiccup and of ague have been often re- 

 moved by it, and it even affects the movements of 

 the heart and arteries ; but in our flcep, all external 

 ftimuli are excluded, and in confequence no furprife 

 can exift. See Section XVII. 3. 7. 



1 8. We frequently awake with pleafure from a 

 dream, which has delighted us, without being able 

 to recollect the tranfaclions of it: unlefs perhaps at 

 a diftance of time, fome analogous idea may intro- 

 duce afrefh this forgotten train : and in our waking 

 reveries we fometimes in a moment loie the train of 

 thought, but continue to feel the glow of pleafure, 

 or the depreflion of fpirits, it occaiioned : whilft at 

 other time we can retrace with eafe thefe hiftories of 

 our reveries and dreams. 



The above explanation of furprife throw* light 

 upon this fubject. When we are fuddenly awaked 

 by any violent ftimulus, the furprife totally difunites 

 the trains of our fleeping ideas from thefe of our 

 waking ones ; but if we gradually awake, this does 

 not happen ; and we readily unravel the preceding 

 trains of imagination. 



19. There are various degrees of furprife; the 

 pi ore intent we are upon the train of ideas, which 



we 



