366 OF SLEEP. SECT. XVIII. 17. 



than diminifhed during thefe hours of our exidence ; and it is 

 probable that nutrition is aimed entirely performed in fleep ; 

 and that young animals grow more at this time than in their 

 waking hours, as young plants have long fince been obferved to 

 grow more in the night, which is their time of fleep. 



17. Two other remarkable circumdances of our dreaming 

 ideas are their inconfidency, and the total abfence of furprife. 

 Thus we feem to be prefent at more extraordinary metamor- 

 phofes of animals or trees, than are to be met with in the fables 

 of antiquity ; and appear to be tranfported from place to place, 

 which leas divide, as quickly as the changes of fcenery are per* 

 formed in a play-houfe ; and yet are not fenfible of their in- 

 confi Hence, nor in the lead degree affe&ed with furprife. 



We muft confider this circumftance more minutely. In our 

 waking trains of ideas, thofe that are inconfiftent with the ufual 

 order of nature, fo rarely have occurred to us, that their con- 

 nexion is the flighted of all others : hence, when a confident 

 train of ideas is exhauded, we attend to the external dimuli r 

 that ufually furround us, rather than to any inconfident idea, 

 which might otherwife prefent itfelf : and if an inconfiftent 

 idea diould intrude itfelf, we immediately compare it with the 

 preceding one, and voluntarily reject the train it would intro- 

 duce ; this appears further in the Section on Reverie, in which 

 (late of the mind external dimuli are not attended to, and yet 

 the dreams of ideas are kept confident by the efforts of volition. 

 But as our faculty of volition is fufpended, and^all external dim- 

 uli are excluded in Jleep,,this flighter connexion of ideas takes 

 place ; and the train is faid to be inconfident ; that is, diflimU 

 lar to the ufual order of nature. 



But, when any confident train of fenfitive or voluntary 

 ideas is flowing along, if any external dimulus afreets us fo vio- 

 lently, as to int'.uJe irritative ideas forcibly into the mind, it 

 difunites the former train of ideas* and we are affected with fur- 

 prife. Thefe dimuli of unufual energy or novelty nor only dif- 

 unite our common trains of ideas, but the trains of mufcular mo- 

 tions alfo, which have not been long edabliflied by habit, ar,d 

 difturb 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 fleep, all external dimuli are excluded, and 

 in confequnce no furprife can exid. 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 tranfac- 

 tions of it ; unlefs perhaps at a didance of time, fome analogous 

 idea may introduce afrefli this forgotten train : and in our wa- 



king 



