330 
ON  FERMENTATION. 
globules  or  very  short  articulations,  either  isolated  or  in  threads, 
constituting  irregular  flocculent  particles.  The  globules  are  very 
much  smaller  than  those  of  beer-yeast,  and  also  present  the 
Brownian  motion.  When  washed  with  a  large  quantity  of  water, 
and  then  disseminated  throughout  some  pure  solution  of  sugar, 
acidification  is  produced  immediately,  and  progresses,  though 
very  gradually,  in  consequence  of  the  acid  interfering  with  the 
influence  of  the  ferment  upon  the  sugar.  But  when  chalk  is 
added,  so  as  to  keep  the  liquid  neutral,  the  transformation  of  the 
sugar  is  much  accelerated ;  and,  even  when  operating  with  a 
very  small  quantity  of  substance,  in  less  than  an  hour  ,the  dis- 
engagement of  gas  becomes  evident,  while  the  liquid  becomes 
charged  with  lactate  and  butyrate  of  lime.  A  very  small  quan- 
tity of  this  ferment  is  sufficient  to  effect  the  transformation  of 
a  large  amount  of  sugar. 
Hence,  M.  Pasteur  infers  that  the  lactic  fermentation  resem- 
bles the  alcoholic  fermentation,  in  being  an  act  correlative  to  the 
production  of  a  nitrogenous  substance,  which  has  all  the  charac- 
ters of  a  micodermic  organism,  probably  very  similar  to  that  of 
beer-yeast.  But  the  difficulties  and  complexity  of  the  subject 
are  far  from  being  resolved  by  this  fact.  Lactic  acid,  although 
the  principal  product  of  the  fermentation  called  lactic,  is  far 
from  being  the  only  one.  It  is  always  accompanied  by  butyric 
acid,  alcohol,  mannite,  and  a  viscous  substance,  the  relative  pro- 
portion of  these  substances  being  subject  to  the  most  capricious 
variations.  With  regard  to  mannite,  a  very  remarkable  circum- 
stance was  observed — when  substituted  for  sugar  in  the  lactic 
fermentation,  all  other  conditions  remaining  the  same,  alcohol  is 
produced,  together  with  lactic  acid  and  butyric  acid,  by  the  fer- 
mentation of  the  mannite.  This  fact  appears,  at  first  sight, 
inconsistent  with  the  production  of  mannite  in  lactic  fermenta- 
tion, at  least  it  might  be  supposed  that  it  would  be  decomposed 
again.  But  this  apparent  inconsistency  is  removed  by  a  more 
close  examination. 
Thus,  when  the  lactic  ferment  has  been  washed  with  a  large 
quantity  of  water,  and  placed  in  contact  with  a  solution  of  pure 
sugar,  the  transformation  of  the  sugar  decreases  as  the  acidity 
of  the  liquid  increases.  By  the  analysis  of  the  liquid,  after 
neutralizing  the  acid  with  chalk  and  decomposing  the  residual 
