Respiration , and the Vfe ef the Blood. 243 
was rendered in fome degree wholefome by the procefs ; 
being, after this, considerably diminished by nitrous air, 
which is a State to which it is brought by agitation in 
water, and which, continued longer, deprives it of its in- 
flammability likewife. It cannot be doubted, therefore, 
but that, in both thefe cafes, the red blood, by becoming 
black, received phlogifton from thefe two kinds of air. 
With refpedt to the phlogifticated air, I only obferved 
that, aftei a few hours expofure to the red blood, it was 
fenfibly, but not much, diminished by nitrous air, which 
otherwife it would not have been in the lead: degree. 
This blood, however, was of the lightest colour; that is, 
according to my hypothefis, the molt free from phlo- 
.gifton, of any that I have ever Seen ; and I have tried the 
fame thing, without fuccefs, with blood of a lefs florid 
colour, though as florid as the common air could make it. 
But it Should be confidered, that the proper function of the 
blood is not to receive phlogiston from air, not meeting 
with any phlogifticated air in the courfe of its circula- 
tion, but to communicate phlogifton to air; and there- 
fore, there is by no means the fame reafon to expert, that 
air will be mended by red blood, as that it will be injured 
by black blood. 
It may be objected to this hypothefis, concerning the 
ufe of the blood, that it never comes into actual contact 
with the air in the lungs, but is Separated from it, though 
as Dr. hales States it, at the diftance of no more than a 
thousandth part of an inch. The red globules alfo Swim 
I i 2 
in 
