65 OF STIMULUS ' Sect. XII. 5. 4. 



As the pains, which originate from defect of ftimulus, only* 

 occur in thofe parts of the fyftem, which have been previously 

 fubjecTed to perpetual flimulus j and as an accumulation of fen~ 

 icrial power is produced in the quiefcent organ along with the 

 pain, as in cold cr hunger, there is rcafon to believe, that the 

 pain i< owing to the accumulation of fenforial power. For, in 

 the locomotive mufcles, in the retina of the eye, and other or- 

 gans of fenle, no pain occurs from the abfence of flimulus, nor 

 any great accumulation of fenforial power beyond their natural 

 quantity, fince thefe organs have not been ufed to a perpetual 

 flipply of it. There is indeed a greater accumulation occurs in 

 the organ of virion after its quiefcence, becaufe it is fubject to 

 more conitant flimulus. 



4. A certain quantity of flimulus lefs than natural induces 

 the moving organ into feebler and more frequent contractions, 

 as mentioned in No. I. 4. of this Section. For each contraction 

 moving through a lefs fpace, or with lefs force, that is, with lefo 

 expenditure of the fpirit of animation, is fooner relaxed, and the 

 fpirit of animation derived at each interval into the acting fibres 

 being lefs, thefe intervals likewife become fhorter. Hence the 

 tremors of the hands of people accuitomed to vinous fpirit, till 

 they take their ufual ftimulus •, hence the quick pulfe in fevers 

 attended with debility, which is greater than in fevers attended 

 with ftrength ; in the latter the pulfe feldom beats above 120 

 times in a minute, in the former it frequently exceeds 140. 



It mufl be obferved, that in this and the two following arti- 

 cles the decrealed action of the fyftem is probably more fre- 

 quently occafioned by deficiency in the quantity of fenforial 

 power, than in the quantity of ftimulus. Thus thofe feeble 

 conftitutions which have large pupils of their eyes, and all who 

 labour under nervous fevers, feem to owe their want of natural 

 quantity of activity in the fyftem to the deficiency of fenforial 

 power ; fince, as far as can be feen, they frequently poiTefs the 

 natural quantity of ftimulus. 



5. A certain quantity of ftimulus, lefs than that above men- 

 tioned, inverts the order of fuccelTive fibrous contractions ; as 

 in vomiting the vermicular motions of the ftomaeh and duode- 

 num are inverted, and their contents ejected, which is probably- 

 owing to the exhauftion of the fpirit of animation in the acting 

 mufcles by a previous excefiive ftimulus, as by the root of ipecac- 

 uanha, and the cenfequent defect of fenforial power. The 

 lame retrograde motions afreet the whole inteftinal canal in 

 aleus ; and the cefophagus in globus hyftericus. See this fur- 

 ther explained in Seel. XXIX. No. 11. on Retrograde Motions. 



I muft obferve, alfo, that fumcthing fimilar happens in the 



production 



