SECT. VIII. 3. SENSITIVE MOTIONS. 45 



been formerly excited by the objefts of thefe fenfa- 

 tions, now vividly recur before us by their connec- 

 tion with thefe fenfations themfelves. So the fair 

 fmiling virgin, that excited your love by her pre- 

 fence, whenever that fenfation recurs, rifes before 

 vou in imagination ; and that with all the pleafing 

 circumftances, that had before engaged your atten- 

 tion. And in fleep, when you dream under the in- 

 fluence of fear, all the robbers, fires, and precipices, 

 that you formerly have feen or heard of, arife be- 

 fore you with terrible vivacity. All thefe fenfuai 

 motions, like the mufcular ones above mentioned, 

 are performed with ftrength and velocity in pro- 

 portion to the energy of the fenfation of pleafure 

 or pain, which excites them, and the quantity of 

 fenforial power. 



III. i. Many of thefe mufcular motions above 

 defcribed, that are mod frequently excited by our 

 fenfations, are neverthelefs occafionally caufable by 

 volition ; for we. can frnile or frown ipontaneoufly, 

 can make water before the quantity or acrimony of 

 the urine produces a difagreeable fenfation, and can 

 voluntarily rnaflicate a naufeous drug, or fwallow a 

 bitter draught, though our fenfation would ftrongly 

 diffuade us. 



2. In like manner the fenfuai motions, or ideas, 

 that~are mod frequently excited by our fenfations, 

 are neverthelefs occafionally caufeable by volition, 

 as we can fponcaneoufly call up laft night's dream 

 before us, tracing it induftrioufly ftep by ftep 

 through all its variety of fcenery and t ran faction ; 

 or can voluntarily examine or repeat the ideas, that 

 have been excited by our difgutt or admiration. 



III. i. Innumerable trains or tribes of motions 

 are affociated with thefe fenfitive mufcular motions 

 above mentioned ; as when a drop of water failing 

 into the wind-pipe difagreeably affects the air-veflcis 

 of the lungs, they are excited into violent aclion ; 



E 2 and 



