534 OXYGENATION OF BLOOD. SECT. XXXVIII. i. 



ration the oxygene of the air unites with the phlo- 

 giftic part of the blood, and probably produces 

 phofphoric or animal acid, changing the colour of 

 the blood from a dark to a bright red ; and proba- 

 bly fome of the matter of heat is at the fame time 

 given put according to the theory of Pr. Craw- 

 ibrd. But as the evolution of heat attends almoft 

 all chemical combinations, it is probable, that it 

 alfo attends the fecrerions of the various fluids from 

 the blood ; and that the conftant combinations or 

 productions of new fluids by mearjs of the glands 

 conftitute the more general fource of animal beat ; 

 this feems evinced by the univerfal evolution of the 

 matter of heat in the blufh of fharne or of anger ; in 

 which at the fame time an increafed fecretion of the 

 perfpirable matter occurs ; and the partial evolution 

 of it from topical inflammations, as in gout or rheu- 

 matifm, }n which there is a fecretion of new blood- 

 veffels. 



Some medical philofophers have ^fcribed the beat 

 of animal bodies to the friction of the particles of 

 the blood againft the iides of the vefiels. But no 

 perceptible heat has ever been produced by the agi- 

 tation of water, or oil, or quickfilver, or other 

 fluids ; except thofe fluids have undergone at the 

 fame time fome chemical change, as in agitating 

 milk or wine, till they become four. 



Befides the fuppofed production of phofphorie 

 acid, and change of .colpur of the blood, and the 

 production of carbonic acM, there would appear to 

 be fomething of a more ftjbtile nature perpetually 

 acquired from the atrnofphere ; which is too fine 

 to be long contained in animal veffels, and there- 

 fore requires perpetual renovation ; and without 

 which life cannot continue longer than a minute or 

 two ; this ethereal fluid is probably fecreted from 

 the blood by the brain, and perpetually diflipated 

 in the aclions of ihe mufcles and organs of fenfe. 



That 



