Emergence
of
Virology
To
understand
the
mechanism
of
disease
development,
Pasteur
and
his
colleagues
were
testing
infectious
fluids
for
the
presence
of
disease
producing
agents
by
passing
them
through
filters
able
to
retain
bacterial
cells.
If
the
filtrates
no
longer
produced
infection,
the
presence
of
a
bacterial
agent
in
the
original
fluid
and
the
disease
was
suspected.
Porcelain
filters
that
allowed
the
passage
of
fluid
but
not
bacteria
were
first
developed
by
Chamberland
in
1884
and
were
found
useful
in
sterilization
of
liquids.
The
use
of
such
filters
also
made
it
possible
to
know
whether
infective
agents
smaller
than
the
bacteria
exist.
In
1892,
the
Russian
scientist
Iwanowski's
applied
this
test
using
an
extract
from
tobacco
plants
infected
with
mosaic
disease
and
found
that
the
filtrate
was
fully
infectious
to
healthy
plants.
