H SENSITIVE MOTIONS. SECT. VIII. r 



the fame time accompanied with painful or pleafur- 

 able fenfations ; and at length become by habit 

 caufable by the fenfations. Thus the motions of 

 the fphincters of the bladder and anus were origi- 

 nally excited into action by irritation ; for young 

 children give no attention to thefe evacuations ; 

 but as foon as they become fenfible of the inconve- 

 nience of obeying thefe irritations, they fuffer the 

 water or excrement to accumulate, till it difagree- 

 ably affects them ; and the action of thofe fphinc- 

 ters is then in confequence of this difagreeable fen- 

 fation. So the fecretion of faliva, which in young 

 children is copioufly produced by irritation, and 

 drops from their mouths, is frequently attended 

 with the agreeable fenfation produced by the maf- 

 tication of tafteful food ; till at length the fight of 

 fuch food to a hungry perfon excites into action 

 thefe falival glands j as is feen in the flavering of 

 hungry dogs. 



The motions of thofe mufcles, which are affected 

 by lafcivious ideas, and thofe which are exerted in 

 fmiling, weeping, flatting from fear, and winking 

 at the approach of danger to the eye, and at times 

 the actions of every large inufcle of the body be- 

 come caufable by our fenfations. And all thefe mo- 

 tions are performed with ftrength and velocity in 

 proportion to the energy of the fenfation that 

 excites them, and the quantity of fenforialower. 



2. Many of the motions of our organs of fenfe, 

 or ideas, that were originally excited into action by 

 irritation, become in like manner more frequently 

 caufable by our fenfations of pleafure or pain. Theie 

 motions are then termed the ideas of imagination, 

 and makeup all the fcenery and tranfactions of our 

 dreams. Thus when any painful or pleafurable fen- 

 fations poflefs us, as of love, anger, fear ; whether 

 in our fleep or waking hours, the ideas, that have 



been 



