36 FIBROUS CONTRACTIONS. SECT. VI. i, 



Js-mm ii^j "i \i> Taaofmxa a* srvfo, . 



SECT. VL 



OF THE FOUR CLASSES OF FIBROUS MOTIONS. 



i* *JS ' i 



I. Origin of fibrous contractions. II. Diftribution of 

 them into four c/qffes, irritative motions y fenfit'we mo* 

 tions, 'voluntary motions, and officiate motions, defined. 



I. ALL the fibrous contractions of animal bodies 

 originate from the fenforium, and refolve them- 

 felves into four clafles, correfpondent with the four 

 powers or motions of the fenforium above defcrib- 

 ed, and from which they have their caufation. 



1. Thefe fibrous contractions were originally 

 caufed by the irritations excited by objects, which 

 are external to the moving organ. As the pulfati- 

 ons of the heart are owing to the irritations excited 

 by the ftimulus of the blood ; and the ideas of per- 

 ception are owing to the irritations excited by ex- 

 ternal bodies. 



2. But as painful or pleafurable fenfations fre- 

 quently accompanied thofe irritations, by habit thefe 

 fibrous contractions became caufable by the fenfa- 

 tions, and the irritations ceafed to be neceflary to 

 their production. As the fecretion of tears in grief 

 is caufed by the fenfation of pain ; and the ideas of 

 imagination, as in dreams or delirium, are excited 

 by the pleafure or pain, with which they were for- 

 merly accompanied. 



3. But as the efforts of the will frequently ac- 

 companied thefe painful or pleafurable fenfations, by 

 habit the fibrous contractions became caufable by 

 volition ; and both the irritations and fenfations 

 ceafed to be neceflary to their production. As the 



deliberate 



