On the Operation of Medicines. 1 1 5 



is carried into the thoracic duft, and there mixed 

 with a large portion of the chyle and lymph, by 

 which its acrimony is fheathed and diluted, or 

 its chemical properties changed, before it enters 

 the mafs of blood ? For the abforbents of the 

 fkin, and of the inteftines, fhould feem to 

 require a capacity to bear the ftimulus of thofe 

 extraneous bodies to which, in both fituations, 

 they are expofed. 



III. Medicines introduced into the courfe of 

 circulation may afFe6t the general conftitution 

 of the fluids; produce changes in their particular 

 qualities ; fuperadd new ones ; or counteract the 

 morbific matter, with which they may be occa- 

 fionally charged. By obfervations on the 

 hsemorrhages, which have been fuftained with- 

 out deftrudlion to life; from experiments made 

 on animals, by drawing forth all their blood ; 

 and by a compution of the bulk of the arteries 

 and veins*; the mafs of circulating fluids has 

 been eftimated at fifty pounds, in a middle-fized 

 man ; of which twenty-eight pounds are fuppofed 

 to be red blood. Fluids, bearing fo large a 

 properties to the weight of the whoje body, 

 have afl"uredly very important offices in the 

 animal ceconomy. Endued with the common 

 properties of other fluids, they are fubjedt to 

 mechanical laws ; being varioufly compounded, 



* Vid. Halleri Prim. Lin. fedt. CXLIX. 



P 4 they ' 



