4+6 THEORY OF FEVER. SUP. I. i. i 



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for a minute, thcfe capillary veflels and their glands become tor- 

 pid or quiefcent, Owing to the eduction of the ftimulus of heat. 

 The fkin then becomes pale, becaufe no blood pafles through the 

 external capillaries ; and appears fhrunk, becaufe their fides are 

 collapfed from inactivity, not contracted by fpafm ; the roots 

 of the hair are left prominent from the feceding or fubfiding of 

 the (kin around them ; and the pain of coldnefs is produced. 



In this fituation, if the ufual degree of warmth be applied, 

 thefe veflels regain their activity ; and having now become 

 more irritable from an accumulation of the fenforial power of 

 irritation during their quiefcence, a greater exertion of them fol- 

 lows, with an increafed glow of the {kin, and another kind of pain, 

 which is called the hot-ach ; but no fever, properly fo called, is 

 yet produced ; as this effect is not univerfal, nor permanent, 

 nor recurrent. 



2. If a greater part of the, cutaneous capillaries with their 

 mucous and perfpirative glands be expofed for a longer time to 

 cold, the torpor or quiefcence becomes extended by direct fym- 

 pathy to the heart and arteries ; which is known by the weak- 

 nefs, and confequent frequency of the pulfe in cold fits of fever. 



This requires to be further explained. The movements of 

 the heart and arteries, and the whole of the circulatory veflels, 

 are in general excited into action by the two fenforial powers of 

 irritation, and of aflbciation. The former is excited by ftimu- 

 lus, the latter by the previous actions of a part of the vital circle 

 of motions. In the above fituation the capillaries act weakly 

 from, defect of irritation, which is caufed by deficient ftimulus 

 of heat ; but the heart and arteries act weakly from defect of 

 aflbciation, which is owing to the weak action of the capilla- 

 ries j which does not now excite the fenforial power of aflbcia- 

 tion into action with fuflicient energy. 



After a time, either by the application of warmth, or by the 

 increafe of their irritability owing to the accumulation of the 

 fenforial power of irritation during their previous quiefcence, the 

 capillary veflels and glands act with greater energy than natural; 

 whence' the red colour and heat of the fkin. The heart and ar- 

 teries acquire a greater ftrength of pulfation, and continue the 

 frequency of it, owing to the accumulation of the fenforial pow- 

 er of aflbciation during their previous torpor, and their confe- 

 quent greater aflbciability j which is nowalfo more ftrongly ex- 

 cited by the increafed actions of the capillaries. And thus a 

 fit of fimple fever is produced, which is termed Febris irritati- 

 va ; and confifts of a torpor of the cutaneous capillaries with 

 their mucous and peripirable glands, accompanied with a tor- 



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