20 ANIMAL CAUSATION. Sect. IV. 



SECT. IV. 



LAWS OF ANIMAL CAUCATION. 



I. The fibres, which conftitute the mufcles and organs of 

 fenfe, pofTefs a power of contraction. The circumftances at- 

 tending the exertion of this power of contraction conftitute 

 the laws of animal motion, as the circumftances attending the 

 exertion of the power of attraction conftitute the laws of 

 motion of inanimate matter. 



II. The fpirit of animation is the immediate caufe of the 

 contraction of animal fibres, it refides in the brain and nerves, 

 and is liable to general or partial diminution or accumulation. 



III. The ftimulus of bodies external to the moving organ is 

 the remote caufe of the original contractions of animal fibres. 



IV. A certain quantity of ftimulus produces irritation, which 

 is an exertion of the fpirit of animation exciting the fibres into 

 contraction. 



V. A certain quantity of contraction of animal fibres, if it be 

 perceived at all, produces pleafure ; a greater or lefs quantity of 

 contraction, if it be perceived at all, produces pain ; thefe con- 

 ftitute fenfation. 



VI. A certain quantity of fenfation produces defire or aver- 

 fion ; thefe conftitute volition. 



VII. All animal motions which have occurred at the fame 

 time, or in immediate fucceflion, become fo connected, that 

 when one of them is reproduced, the other has a tendency to 

 accompany or fucceed it. When fibrous contractions fucceed 

 or accompany other fibrous contractions, the connexion is term- 

 ed afibciation ; when fibrous contractions fucceed fenforial mo- 

 tions, the connexion is termed caufation j when fibrous and fen- 

 foriarl motions reciprocally introduce each other, it is termed 

 catenation of animal motions. All thefe connexions are faid to 

 be produced by habit, that is, by frequent repetition. Thefe 

 laws of animal caufation will be evinced by numerous facts, 

 which occur in our daily exertions ; and will afterwards be em- 

 ployed to explain the more recondite phenomena of the produc- 



n, growth, difeafes, and decay of the animal fyftem. 



SECT. 



