,£ect. VIII. i.i. SENSITIVE MOTIONS. ^ 



SECT. VIII. 



OF SENSITIVE MOTIONS. 



I. I . Serf five mufcular motions were originally excited into action 

 by irritation, 2. Andfenfitive fenfual motions, ideas of imagina- 

 tion, dreams. II. I. Senjitive mufcular motions are occafonally 

 obedient to 'volition. 2. And fenfttive fenfual motions. III. I. 

 Other mufcular motions are officiated with the fenfitive ones, 2- 

 And other fenfual motions. 



1. I. Many of the motions of our mufcles, that are excited 

 into action by irritation, are at the fame time accompanied with 

 painful or pleafurable fen fat ions ; and at length become by 

 habit caufable by the fenfations. Thus the motions of the 

 fphincters of the bladder and anus were originally excited into 

 action by irritation ; for young children give no attention to 

 thefe evacuations ; but as foon as they become fenfible of the 

 inconvenience of obeying thefe irritations, they fuffer the water 

 or excrement to accumulate, till it difagreeably affects them 5 

 and the action of thofe fphincters is then in confequence of this 

 difagfeeable fenfation. 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 maftication of tafteful food ; till at 

 length the fight of fuch food to a hungry perfqn excites into 

 action thefe falival glands ; as is (sen in the Havering of hungry 

 dogs. 



The motions of thofe mufcles, which are affected by lafcivi- 

 ous ideas, and thofe which are exerted in fmiling, weeping, 

 flarting from fear, and winking at the approach of clanger to 

 the eye, and at times the actions of every large mufcle of the 

 body become caufable by our fenfations. And all thefe motions 

 are performed with ilrength and velocity in proportion to the 

 energy of the fenfation that excites them, and the quantity of 

 fenforial power. 



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. Thefe motions are then termed the ideas of imagina- 

 tion, and make up all the fcenery and tranfactions of our 

 dreams. Thus when any painful or pleafurable fenfations pof- 

 fefs us, as of love, anger, fear ; whether in our fleep or waking 

 hours, the ideas, that have been formerly excited by the objects 



of 



