76 OF STIMULUS AND EXERTION. SECT. XII. 2- 



introduces pleafure or pain ; which in their active 

 flate are termed fenfation ; which is another feiifo- 

 rial faculty, and occafionally produces contraction 

 of the fibres ; this pleafure or pain is therefore to 

 be confidered as another ftimulus, which may either 

 act alone or in conjunction with the former faculty 

 of the fenforium termed irritation. This new fti- x 

 mulus of pleafure or pain either induces into action 

 the fenforial faculty termed fenfation, which then 

 produces the contraction of the fibres ; or it intro- 

 duces defire or averiion, which excite into action 

 another fenforial faculty, termed volition, and 

 may therefore be confidered as another ftimulus, 

 which either alone, or in conjunction with one or 

 both of the two former faculties of the fenforium, 

 produces the contraction of animal fibres. There 

 is another fenforial power, that of affociation, 

 which perpetually, in conjunction with one or more 

 of the above, and frequently fingly, produces the 

 contraction of animal fibres, and which is itfelf 

 excited into action by the previous motions of con- 

 tracting fibres. 



Now as the fenforial power, termed irritation, 

 refiding in any particular fibres, is excited into ex- 

 ertion by the ilimulus of external bodies acting on 

 thofe fibres; the fenforial power, termed fenfation, 

 refiding in any particular fibres is excited into exer- 

 tion by the (limulus of pleafure or pain acting on 

 thofe fibres; the fenforial power, termed volition, 

 refiding in any particular fibres is excited into ex- 

 ertion by the ftimulus of deiire or averfion ; and 

 the fenforial power termed affociation, refiding in 

 any particular fibres, is excited into action by the 

 iUmuius of other fibrous motions, which had fre- 

 quently preceded them. The word ilimulus may 

 therefore be ufed without impropriety of language, 

 for any of thefe four caufes, which excite the four 



fenforial 



