Of  viewing  the  Current
134
fiér  :  whereby  the  Sun’s  Rays  reflected  from
the  Looking-glaſs,  through  the  Tube,  upon
the  Object,  pass  on  through  the  Magnifier,
and  exhibit  upon  the  Screen  an  Image  of
the  Object  most  prodigiously  enlarged.  This
I  hope  may  give  some  Idea  of  our  Instrument: ¬
  and  now  I  come  to  the  Application.
Our  Object  was  a  Frog,  whoſe  Limbs
being  extended  and  fastened  on  the  Frame,
we  opened  the  Skin  of  the  Belly  from  near
the  Anus  to  the  Throat;  then  giving  it  a
little  Snip  sideways  both  at  the  Top  and
Bottom,  by  sticking  a  Fish-Hook  in  each
Corner  of  the  Skin,  it  was  easily  stretched
out  before  the  Microscope,  and  presented  on
the  Screen  a  most  beautiful  Picture  of  the
Veins  and  Arteries  in  the  Skin,  with  the
Blood  circulating  through  them.  In  the
Arteries  we  could  plainly  perceive  the  Blood
stopping,  and  as  it  were  receding  a  little,  at
each  Dilatation  of  the  Heart,  and  then  immediately ¬
  rushing  forwards  again  at  each
Contraction;  whilst  in  the  Veins  it  rolled
on  in  a  continual  Current  with  inexpressible
Rapidity  *.
After  considering  this  as  long  as  we
thought  needful,  we  opened  the  Abdomen,
and  extending  the  Muscles  before  the  Micro* ¬
  When  the  Arteries  were  magnified  very  much,  by  re
moving  the  Screen  to  a  considerable  Distance,  the  alternate
Expansion  and  Contraction  of  their  Sides  were  very  visible
and  remarkable.
scope,