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Dr. Boerhaave obferves, may be confidered as a 
chaos containing particles of all kinds of matter. 
And, here it may be obferved, that the feveral fluids 
that are diflblved in the air, will probably aflafl: in 
diflblving and taking up the fubtile effluvia, which 
are carried off from volatile bodies. The air, we find, 
is neceflary for the prefervation of animal lifej but 
when it has palled two or three times through the 
lungs of an animal, it becomes unfit for refpiration, 
and an animal inclofed in fuch air will foon expire ; 
whether the air we breathe depofites in our lungs any 
kind of matter neceffary to the fupport of life, I can- 
not pretend to judge. But I think we may be fure 
that one purpofe for which air was defigned, is the 
carrying off that rnoifture, and other perfpirable 
matter, which conftantly exhales from the lungs. 
Now as air lofes nothing of its elafticity, by pafflng 
through the lungs, it will flill continue fit for fuch 
purpofes, in the animal oeconomy, as may be anfwer- 
ed by the alternate expanfion and contraction of the 
lungs in refpiration. And, therefore, I believe that 
air is rendered unfit for refpiration, chiefly by being 
faturated with that moiflure, and other perfpirable 
matter, which it meets with in the lungs, and 
thereby lofing its power of diflblving, and carrying 
off any more of that kind of matter, which will then 
continually increafe and clog the lungs, fo that an 
animal inclofed in fuch air will die, perhaps fome- 
what in the fame manner, though not fo quickly as 
if it had been drowned. 
Does it not feem probable that, in the conflant 
and quick evaporation of moiflure from the lungs, 
ioiue degree of cold may be produced, as it is in 
other 
