Chap. VI. Of Fevers in general 25 



I middle, the Water that runs on each Side will move with 

 j greater Rapidity than that which is either before or behind. 

 From all which it is evident, that Obftructions in the 

 fmall Capillary Arteries, as they are the Caufe of a greater 

 and more violent Motion of the Blood in thofe that are 

 larger, muft occaiion a Fever ; but efpecially as fuch a 

 Motion may bring on a fubfequent Rarefad:ion in the 

 Blood ; becaufe whatever agitates the Blood, and puts it 

 in a more than ordinary degree of Motion, m.uil: occa- 

 fion more frequent Contradions of the Heart, and alfo 

 of the Arteries, whereby the Blood muft, without doubt, 

 be communicated, and its Parts render'd more fmall. In 

 like mianner an over- great Rarefaction may be the Caufe 

 of a Coagulation of the Blood ; that is, when the Blood 

 happens to be too much rarefy 'd, as in the beginning of 

 a legitimate Fever, the thin Seru?n being expended in a 

 greater than ordinary Quantity, will leave the remaining 

 Mais thicker^ and more unapt to motion, whereby fe- 

 veral Changes and Alterations may be reafonably expe6l- 

 ed : And now lince the Extremities of the Veins, which 

 icommunicate with thofe of the Arteries, are but little dif- 

 ferent from the Arteries thcmfelves, fave only that they 

 ,take a contrary Courfe, and that the Blood moves in them 

 backwards towards the Heart ; whereas in the Arteries it 

 moves from the Heart towards the Extremities : And as 

 the Motion of the Blood in thefe- fmail communicating 

 Branches of the Vein?, is chiefly owing to a continual Suc- 

 ceffion of Blood from the Arteries, when once therefore 

 it gets into them,, its Motion cannot be ealily retarded, 

 unlefs in the Extremities of the Limbs, where its afcent 

 upwards muft, no doubt, be a great Hindrance to it. And 

 this is the Reafon why, in feveral Kinds of Fevers, efpeci- 

 ally in thofe where the Blood happens to be of unequal 

 Compolition, viz. when it is thicker in fome Parts than 

 lOthers, the Puliation of the Arteries muft alfo be unequal ; 

 'becaufe while its grofler Parts are detain'd in the fmalleft 

 Veins and Arteries, the Blood muft move with more Velo- 

 :ity in fome of the other Vellels, for the Rcafons already 

 alledg'd ; but as foon as this Lentor has work'd it felf into 

 :he miOi-e capacious Veins, which grow wider the nearer 

 :hey approach the Heart, and that a tliinner and more at- 

 tenuated Blood fupplies its Place in thofe fmall Branches, 

 '.hen thePulfation becomes more moderate and uniform, 

 ind the Fever is remov'd, at les^ft for that Seafon, 



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