Respiration, and the Ufe of the Bloody 227 
as every other phlogiftic procefs (viz. putrefaction, the 
effervefcenceof iron-filings andbrimftone,orthe calcina- 
tion of metals, See.) affeCts it ; diminifhing the quantity of it 
in a certain proportion, leflening its fpecific gravity, and 
rendering it unfit for refpiration or inflammation, but 
leaving it in a Hate capable of being reflored to a tolerable 
degree of purity by agitation in water, 8cc, Having dis- 
covered this, I concluded, as maybe Seen Phil.Tranf. vol. 
LXII. p. 187. and Obfervations upon Air , vol. I. p. 7 8. 27 7 . 
that the ufe of the lungs is to carry off a putrid effluvium , 
or to difebarge that pblogifton, which bad been taken 
into the Syflem with the aliment, and was become, as it 
were, effete ; the air that is reSpired Serving as a menflruum 
for that purpofe. 
What I then concluded to be the ufe of refpiration in ge- 
neral, I have now, I think, proved to be effected by means 
of the blood, in confequence of its coming So nearly into 
contaCt with the air in the lungs; the blood appearing to 
he a fluid wonderfully formed to imbibe, and part with, 
that principle which the cliemifts call phlogifton, and 
changing its colour in confequence of being charged with 
it, or being freed from it ; and affeCting air in the very 
Same manner, both out of the body and in the lungs ; and 
even notwithftanding the interpofition of various fub- 
ftances, which prevent its coming into immediate con- 
tact with the air. 
As it may not be unpleafing or unufeful, I Shall, 
before I relate my own experiments, briefly recite the . 
principal of the opinions which have been held con- 
Gg 2 
cerning 
