ON  ACETIC  FERMENTATION. 
221 
and  covers  the  surface  of  the  new  liquid.  The  plant  is 
thus  placed  in  exceptional  conditions,  its  vitality  is  very  much 
impaired  if  not  entirely  extinguished.  Experiment  shows  that 
the  plant  under  these  abnormal  circumstances  immediately 
establishes  an  action  between  the  oxygen  of  the  air  and  the  alco- 
hol of  the  liquid.  Acetification  at  once  commences,  and  is  con- 
tinued with  great  activity.  It  is,  however,  ended  in  about  four 
days  by  the  increasing  acidity  of  the  liquid.  If  this  is  replaced 
by  a  fresh  supply  of  dilute  alcohol,  acetification  continues. 
During  this  operation  the  plant  undergoes  a  kind  of  combus- 
tion, which  destroys  its  substance.  In  this  case  the  acetic  acid 
and  the  alcohol  completely  disappear,  and  with  great  rapid- 
ity, the  liquid  becomes  neutral  and  gives  birth  to  divers  in- 
fusorials. 
To  return,  acetification  is  produced  by  a  kind  of  mycoderm. 
2.  According  to  Pasteur,  all  which  has  been  said  upon  the 
influence  of  porous  bodies  in  acetification,  is  erroneous.  The 
following  experiments  support  this  proposition: 
If  dilute  alcohol  is  made  to  flow  for  a  month  along  a  cord,  the 
drops  which  fall  at  the  extremity  of  the  cord  contain  no  acetic 
acid,  but  if  the  precaution  is  taken  of  soaking  the  cord  at  the 
beginning  of  the  experiment  in  a  liquid  upon  whose  surface  is  a 
pellicle  of  mycoderm,  the  alcohol  which  runs  slowly  along  this 
cord  in  contact  with  the  air  becomes  charged  with  acetic  acid. 
According  to  thi3  double  experiment,  the  beech  shavings  used 
in  the  German  process  serve  no  other  purpose  than  that  of  sup- 
porting the  plant. 
In  the  process  such  as  is  used  at  Orleans,  the  acetification,  ac- 
cording to  Pasteur,  is  due  entirely  to  the  almost  insensible 
pellicle  that  covers  the  liquids  in  the  tuns,  which  is  formed  by  the 
smallest  species  of  mycoderm.  The  mother  of  vinegar  will 
have  no  other  influence  upon  the  phenomenon. 
Pasteur  has  shown  that  the  mycoderms  in  presence  of  sugar 
and  not  in  contact  with  oxygen  gas  have  the  power  of  increas- 
ing. Their  respiration  in  that  case  is  probably  effected  by  the 
aid  of  the  oxygen  derived  from  the  sugar. — Journ.  de  Pharm., 
et  de  Ohimie,  1861. 
