Bacterium  aceti. — Cocci,  short  rods,  long  rods,
leptothrix-forms,  and  zoogloea.  Cocci  and  short
rods  may  occur  in  the  same  thread.  The  long
rods  and  threads  may  develop  irregular  swellings,
so-called  involution-forms,  which  have  a  thickened
membrane  and  a  grey  colour.  The  effect  of  the
action  of  this  microbe  is  to  oxidise  alcohol  in  wine
and  other  fruit  juices  into  vinegar.  The  masses  of
zoogloea  united  together  form  a  membranous  layer
which  must  not  be  mistaken  for  the  pellicle  formed
by  Saccharomyces  mycoderma.  The  latter  prepares
the  medium  for  the  action  of  the  Bacterium  aceti.
Bacterium  Pasteurianum,  Hansen. — Morpho-
logically similar  to  Bacterium  aceti,  but  the  cells  contain

*  Zoph,  Die  Spaltyilze.     1885.
278  BACTERIOLOGY.
a  starch-like  substance,  which  is  turned  blue  by  iodine.
They  occur  in  beer-wort.
Bacterium  liodermos  (Bacillus  liodermos,  Fltigge.
Potato  bacterium}. — Short  rods  with  rounded  ends,  motile.
On  plate-cultivations  the  colonies  appear  as  small  white
pellicles  floating  on  liquefied  gelatine.  In  test-tubes  the
gelatine  is  liquefied,  and  the  growth  sinks  down  in  floccu-
lent  masses.  They  occur  on  potatoes,  forming  a  smooth
shining  layer,  which  ultimately  becomes  crumpled.
Bacterium  multipediculum  (Bacillus  multipedi-
culus^  Fliigge). — Long  slender  rods.  They  form  peculiar
insect-like  colonies  on  plate-cultivations.  In  test-tubes
the  appearance  is  less  characteristic.  They  occur  on
potatoes,  forming  a  dirty  yellow  growth.
Bacterium  ramosum  liquefaciens  (Bacillus
ramosus  liquefaciens,  Fliigge). — Rods,  slowly  motile.  They
form  characteristic  colonies  on  plate-cultivations.  The
colonies  gradually  sink  down,  forming  a  well-marked
funnel  with  later  an  appearance  of  concentric  rings.  In
test-tubes  the  funnel-shaped  liquefaction  sends  ofF  rays
into  the  surrounding  gelatine.  They  occur  occasionally,
contaminating  cultivations.
