. XII. 3. OF STIMULUS AND EXERTION. 83 



tremes of exertion and quiefcence, either the fits 

 become lefs and lefs violent from the contractile 

 fibres becoming lefs excitable to the ftimulus by ha- 

 bit, that is, by becoming accuftomed to it, as ex- 

 plained below XII. 3. i. or the whole fenforial 

 power becomes exhaufted, and the arteries ceafe to 

 beat, and the patient dies in the cold part of the 

 paroxyfm. Or fecondly, fo much pain is intro- 

 duced into the fyftem by the violent contractions 

 of the fibres, that inflammation arifes, which pre- 

 vents future cold fits by expending a part of the 

 fenforial power in the exteniion of old vefiels or the 

 production of new ones; and thus preventing the 

 too great accumulation or exertion of it in other 

 parts of the fyftem ; or which by the great increafe 

 of ftimulus excites into great action the whole glan- 

 dular fyilem as well as the arterial, and thence a 

 greater quantity of fenforial power is produced in 

 the brain, and thus its exhauftion in any peculiar 

 part of the fyftem ceafes to be affected. 



4. Or thirdly, in confequence of the painful or 

 pleafurable fenfation above mentioned, defire and 

 averfion are introduced, and inordinate volition 

 fucceeds ; which by its own exertions expends fo 

 much of the fpirit of animation, that the two other 

 fenforial faculties, or irritation and fen far ion, act 

 fo much more feebly ; that the paroxyfms of fever, 

 or that libration between the extremes of exert -'on 

 and inactivity of the arterial fyitem, gradually fub- 

 fides. On this account a temporary infanity is a 

 favourable fign in fevers, as I have had fbme op. 

 portunities of obferving. 



III. Of repeated Stimulus. 



i. When a ftimulus is repeated more frequently 

 than the expenditure of fenforial power can be re- 

 newed in the acting organ, the effect of ihe ftimu- 

 lus 



