jSect. XXXV. r. 3. OP ASSOCIATION. 345 



3. An inftance of the third circumftance, where the primary 

 part of a train of irritative motions acts with lefs, and the fec- 

 ondary part with greater energy, may be cbferved by making 

 the following experiment. If a perfon lies with his arms and 

 fhoulders out of bed, till they become cold, a temporary coryza 



-or catarrh is produced ; fo that the paffage of the noftrils be- 

 comes totally obftructed ; at lead this happens to many people ; 

 and then on covering the arms and (boulders, till they become 

 warm, the pafTage of the noftrils ceafes 2gain to be obftructed, 

 and a quantity of mucus is difcharged from them. In this cafe 

 the quiefcence of the veffels of the fkin of the arms and moul- 

 ders, occafioned by expofure to cold air, produces by irritative 

 affociation an increafed action of the veffels of the membrane of 

 the noftrils ; and the accumulation of fenforial power during the 

 torpor of the arms and (boulders is thus expended in producing 

 a temporary coryza or catarrh. 



Another inftance maybe adduced from the fympathyor con- 

 fent of the motions of the ftomach with other more diitant links 

 of the very extenfive tribes or trains of irritative motions affoci- 

 ated with them, defcribed in Seel. XX. on Vertigo. When 

 the actions of the fibres of the ftomach are diminished or invert- 

 ed, the actions of the abforbent veffels, which take up the mucus 

 from the lungs, pericardium, and other ceils of the body, be- 

 come increafed, and abforb the fluids accumulated in them with 

 greater avidity, as appears from the exhibition of foxglove, anti- 

 mony, or other emetics, in cafes of anafarca, attended with un- 

 equal pulfe and difficult refpiration. 



That the act of naufea and vomiting is a decreafed exertion 

 of the fibres of the ftornach may be thus deduced •, when an 

 emetic medicine is adminiftered, it produces the pain of ficknefs, 

 as a difagreeable tafte in the mouth produces the pain of naufea ; 

 thefe pains, like that of hunger, or of cold, or like thofe, which 

 are ufually termed nervous, as the head-ach or hemicrania, do 

 not excite the organ into greater action •, but in this cafe I im- 

 agine the pains of ficknefs or of naufea counteract or deftroy 

 the pleafurable fenfation, which feems neceffary to digeftion, as 

 .(hewn in Sea. XXXIII. 1. 1. The periftaltic motions of the 



[1 fibres of the ftomach become enfeebled by the want of this 

 ftimulus of pleafurable fenfation, and in confequence flop for a 



r time, and then become inverted ; for they cannot become invert- 

 ed without being prevroufly flopped. Now that this inverfion 



! of the trains of motion of the fibres of the ftomach is owing to 

 the deficiency of pleafurable fenfation is evinced from this cir- 

 cumftance, that a naufeous idea excited by words will produce 

 vomiting as effectually as a naufeous drug. 

 Vol. I. W w Hence 



