SECT. XII. 5. OF STIMULUS AND EXERTION. 97 



derived at each interval into the acting fibres 

 being lefs, thefe intervals likewife become fhorter. 

 Hence the tremours of the hands of people accuf- 

 tomed to vinous fpirit, till they take their ufual 

 flimulus ; hence the quick pulfe 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 muft be obferved, that in this and the two 

 following articles the decreafed action of the fyf- 

 tem is probably more frequently 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 ; 

 iince, as far as can be feen, they frequently poflefs 

 the natural quantity of flimulus. 



5. A certain quantity of ft imulus, lefs than that 

 above mentioned, inverts the order of fucceffive 

 fibrous contractions ; as in vomiting the vermi- 

 cular motions of the ftomach and duodenum 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 

 excefllve flimulus, as by the root of ipecacuanha, 

 and the confequent defect of fenforial power. The 

 fame retrograde motions affect the whole inteftinal 

 canal in ileus ; and the cefophagus in globus hyf- 

 tericus. See this further explained in Sect. XXIX. 

 No. ii. on Retrograde Motions, 



I muft obferve, alfo, that fomething fimilar hap- 

 pens in the production of our ideas, or fenfual 

 motions, when they are too weakly excited 5 when 

 any one is thinking intenfely about one thing, 

 and carelefsly converfing about another, he is 

 liable to ufe the word of a contrary meaning to 



that 



