*44 CATENATION. SECT. XVII. I( 3, 



ated fucceffive irritations, as when we Jearn to repeat the alpha- 

 bet in its order by frequently reading the letters of it. Thus the 

 vermicular motions of the bowels were originally produced by 

 the fucceifive irritations of rhe paffmg aliment ; and the fuccef- 

 fion of actions of the auricles and ventricles of the heart was 

 originally formed by fucceffive ftimulus of the blood, thefe after- 

 wards become part of the diurnal circles of animal actions, as 

 appears by the periodical returns of hunger, and the quickened 

 pulfe of weak people in the evening 



Other catenations of aniiral motion are gradually acquired 

 by fucceffive agreeable fenfations, as in learning a favourite fong 

 or dance ; others by difagreeable fenfations, as in coughing or 

 nictitation ; thefe become affociated by frequent repetition, and 

 afterwards compofe parts of greater circles of action like thofe 

 above mentioned. 



Other catenations of motions are gradually acquired by fre- 

 quent voluntary repetitions ; as when we deliberately learn to 

 march, read, fence, or any mechanic art, the motions of many 

 of our mufcles become gradually linked together in trains, tribes, 

 or circles of action. Thus when any one at firft begins to ufe 

 the tools in turning wood or metals in a lathe, he wills the mo- 

 tions of his hand or fingers, till at length thefe actions become 

 ib connected with the effect, that he feems only to will the 

 point of. the chiffel. Thefe are caufed by volition, connected 

 by affociation like thofe above defcribed, and afterwards become 

 parts of our diurnal trains or circles of action. 



3. All thefe catenations of animal motions are liable to pro- 

 ceed fome time after they are excited, unlefs they are difturbed 

 or impeded by other irritations, fenfations, or volitions 5 and 

 in many inftances in fpite of our endeavours to flop them ; and 

 this property of animal motions is probably the caufe of their 

 catenation. Thus when a child revolves fome minutes on one 

 foot, the fpeftra of the ambient objects appear to circulate round 

 him fome time after he falls upon the ground. Thus the pal- 

 pitation of the heart continues fome time after the object of fear, 

 which ocafioned it, is removed. The blufh of fhame, which is 

 an excefs of ienfation, and the glow of anger, which is an excefs 

 of volition, continue fome time, though the affected perlon finds 

 that thofe emotions were caufed by miftaken facts, and endeav- 

 ours to extingiulh their appearance. See Sect. XII. 1.5, 



4. When a circle of motions becomes connected by frequent 

 repetitions as above, we can exert our attention ftrongly on oth- 

 er objects, and the concatenated circle of motions will neverthe- 

 kfs proceed in diie order ; as whilft you are thinking on this 



fubject 



