Sup. I. 1 1. 6. THEORY OF FEVER. 479 



time ocgafion an increafe of the aflfociate motion of another part, 

 which is catenated with it. 



This circumftance neverthelefs can only occur in thofe parts 

 of the fyllem, whofe natural actions are perpetual, and the ac- 

 cumulation of fenforial power on that account very great, 

 when their activity is much lefTened by the deduction of their 

 ufual (timulus 5 and are therefore only to be found in the fan- 

 guiferous fyftem, or in the alimentarv canal, or in the glands and 

 capillaries. Of the firit of which the following is an inftance. 



The refpiration of a reduced atmofphere, that is of air mixed 

 with hydrogene or azote, quickens the pulfe, as obferved in the 

 cafe of Mrs. Eaton by Dr. Reynolds and Dr. Thornton j to 

 which Dr. Beddoes adds in a note, that " he never faw an in- 

 ftance in which a lowered atmofphere did not at the moment 

 quicken the pulfe, while it weakened the action of the heart 

 and arteries." Confiderations on Factitious Airs, by Thomas 

 Bcctdoes and James Watt, Part III. p. 67. Johnfon, London. 

 By the afliftance of this new fact the curious circumftance of 

 the quick production of warmth of the fkin on covering the 

 head under the bed-clothes, which everv one muft at fome time 

 have experienced, receives a more fa-tisfaclory explanation, than 

 that which is given in Clafs IV. 1. 1.2. which was printed 

 before this part of Dr. Beddoes's Confiderations was published. 



For if the blood be deprived of its accuftomed quantity of ox- 

 ygen, as in covering the head in bed, and thus breathing an air 

 rendered impure by repeated refpiration, or by breathing a fac- 

 titious air with lets proportion of oxygen, which in common ref- 

 piration pafies through the moiit membranes of the lungs, and 

 mixes with the blood, the pulfations of the heart and arteries 

 become weaker, and confequently quicker, by the defect of the 

 ilimulus of oxygen. And as thefe vefTels are fubjt* ct to perpet- 

 ual motion, the accumulation of the fenforial power of irrita- 

 tion becomes fo great by their lefTened activity, that it excites 

 the vefTels next connected, the cutaneous capillaries for im'tance, 

 into more energetic actions, fo as to produce increafed heat of 

 the fkin, and greater perfpiration. 



How exactly this reiembles a continued fever with weak and 

 quick pulfe ! — in the latter the action of the heart and arteries 

 are lefTened by defect of the excitement of the fenforial power of 

 aflociation, owing to the torpor or Ieflened actions of the ftom- 

 ach ; hence the accumulation of the fenforial power of aflocia- 

 tion in this cafe, as the accumulation of that of irritation in the 

 former, becomes fo abundant as to excite into increafed action 

 the parts mod nearly connected, as the cutaneous capillaries. 



In refpect to the circumfcauce mentioned by Sydenham, that 



covering 



