[ xiv ] 
our conftitution. The moft active 
poifons which are known do not 
fo quickly deftroy the life of an ani- 
mal as the want of air, or the 
breathing of it when it is rendered 
highly noxious. It will appear in 
this work, that thofe very plants, 
which, influenced by the light of 
the fun, repair the injury done to 
this fluid by the breathing of ani- 
mals, and by many other caufes, 
may, in different circumftances, poi- 
fon fo much this very element, as 
to render it abfolutely unfit for re- 
_fpiration, and, inftead of keeping up 
life, to eae it in a moment. _ 
Therefore this univerfally-diffufed 
~ element deferves not only the pur- 
fuit of philofophers, but claims 
more immediately the attention of 
thofe whofe profeffion it isto preferve 
health and to cure difeafes, I have 
- -beftowed 
