480 DISEASES OF VOLITION. SECT. XXXIV. i, 



actions, which contribute to remove the caufe of 

 pain are uniformly and invariably exerted, as in 

 coughing or fneezing ; but thofe motions which are 

 exerted in confequence of averfion without contri- 

 buting to remove the painful caufe, but only to pre- 

 Srent the fenfation of it, as in epileptic, or catalep- 

 tic fits are not uniformly and invariably exerted, 

 but change from one fet of mufcles to ano- 

 ther, as will be further explained; and may by this 

 criterion alfo'be diflinguifhed from the former. 



At the lame time thofe motions, which are ex- 

 cited by perpetual ftimulus, or by aflbciation with 

 each other, or immediately by pleafurable or pain- 

 ful fenfation, may properly be termed involuntary 

 motions, as thofe of the heart and arteries ; as the. 

 faculty of volition feldom affects thofe, except when 

 it exifts in unnatural quantity, as in maniacal peo- 

 ple. 



2. It was obferved in Section IV. on the Produc- 

 tion of Ideas, that thofe parts of the fyftem, which 

 are ufually termed the organs of fenfe, are liable 

 to be excited into pain by the excels of the ftimu- 

 lus of thofe objects, which are by nature adapted 

 to affeft them ; as of too great light, found, or 

 preflure. But that thefe organs receive no pain 

 from the defect or abfence of thefe ftimuli, as in 

 darknefs or filence. But that our other organs of 

 perception, which have generally been called appe- 

 tites, as of hunger, thirft, want of heat, want of 

 freih air, are liable to be affected with pain by the 

 defect, as well as by the excefs of their appropri- 

 ated ftimulL 



This excefs or defect of itimulus is however to 

 be confidered only as the remote caufe of the pain, 

 the immediate caufe being the excefs or defe6t of the 

 natural action of the affected part, according to 

 Sect, IV. 5. Hence all the pains of the body may 



be 



