226 
Dr . Priestley’s Obfervations on 
XIII. Obfervations on Refpiration , and the Ufe of the Blood. 
By Jofeph Prieftley, LL.D. F. R. S. 
J am 25,^ | '^HERE is, perhaps, no fubjedt in phyliology, 
and very few in philofophy in general, that 
has engaged more attention than that of the ufe of refpi- 
ration . It is evident, that without breathing moft animals 
would prefently die; and it is alfo well known, that the 
fame air will not long anfwer the purpofe : for if it has 
been frequently refpired, the breathing of it is as fatal as 
the total deprivation of air. But by what property it is, 
that air contributes to the fupportof animal life; and why 
air that has been much breathed will no more anfwer 
the purpofe, feems not to have been difcovered by any of 
the many philofophers and phylicians who have pro- 
fefledly written upon the fubjedt; and it might have con- 
tinued to elude all direB invefligation , when it difcovered 
itfelf, without any trouble or thought, in the courfe of 
my refearches into the properties of different kinds of 
air, which had at flrlf quite another object. 
In thefe experiments it clearly appeared, that refpiration 
is a phlogiflic procefs , affecting air in the very lame manner 
as 
