IV 
PREFACE. 
II. 
"The Air is a principal Agent of Motion 
thro all Nature , and may be called the Spring 
of all moveable Bodies. No Animal can move 
07i the Earth , in the Atmofphere , or Waters , 
without its kindly Affiftance ; not can there be 
any Growth of either Animal or Vegetable 
Bodies ; a#/*/} promoted by this mofl iifeful Ele- 
ment : In fhort the Phenomena in Nature 
are numberlefs , that necejjarily require its Aid. 
In this Light , I find it highly concerned in the 
AElions of Animals ; which , I think, will clearly 
appear by the Ufe I make of it in accounting for 
thofe of their Mufcles : And I find , that with- 
out fuppofing it fo 9 no probable Conjeciut.es can 
be produced towards accounting for that Motion, 
which a Review of the fever al Opinions of the 
Authors mentioned in my fir ft Leffiure will fuf- 
ficiently teftify. 
III. 
What the Soul is, or in what Maimer floe 
makes her Impulfe on thofe Parts of Animals 
that 
