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0308
托福试题
阅读(
55minutes
)
Question1-11
If
food
is
allowed
to
stand
for
some
time,
it
putrefies.Whentheputrefiedmaterial
is
examined
microscopically
,it
is
found
to
be
teemingwithbacteria.Wheredothese
bacteria
come
from
,
since
they
are
not
seen
in
freshfood?Evenuntilthemid-nineteenth
century,
many
people
believed
that
such
microorganismsoriginatedbyspontaneous
(5
)
generation
,a
hypothetical
process
by
which
livingorganismsdevelopfromnonliving
matter.
The
most
powerful
opponent
of
the
theory
of
spontaneous
generation
was
the
French
chemist
and
microbiologist
Louis
Pasteur(1822-1895).Pasteur
showedthatstructures
present
in
air
closely
resemble
the
microorganisms
seeninputrefyingmaterials.Hedid
(10)
this
by
passing
air
through
guncotton
filters,
thefibersofwhichstopsolidparticles.After
theguncottonwasdissolvedinamixtureofalcohol
andether,theparticlesthatithad
trapped
fell
to
the
bottom
of
the
liquid
and
were
examinedonamicroscopeslide.Pasteur
foundthatinordinaryairtheseexistsavarietyof
solidstructuresranginginsizefrom
0.01
mm
to
more
than
1.0
mm.Many
of
these
bodies
resembledthereproductive
(15)
structuresofcommonmolds,single-celledanimals,
andvariousothermicrobialcells.
As
many
as
20
to
30
of
them
were
found
in
fifteen
