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  The 
  Enzymes 
  of 
  B. 
  coli 
  communis. 
  

  

  with 
  more 
  hydrogen 
  available, 
  acetic 
  acid, 
  and 
  with 
  still 
  more, 
  alcohol. 
  The 
  

   proportions 
  in 
  which 
  the 
  products 
  of 
  Group 
  2 
  appear 
  depends 
  therefore 
  on 
  

   the 
  intimacy 
  with 
  which 
  the 
  reactions 
  of 
  this 
  group 
  co-operate 
  with 
  the 
  

   reactions 
  of 
  Group 
  1, 
  and 
  this 
  further 
  explains 
  the 
  fact 
  that, 
  in 
  many 
  normal 
  

   fermentations, 
  there 
  is 
  a 
  tendency 
  for 
  Groups 
  2 
  and 
  3 
  to 
  appear 
  as 
  con- 
  

   stituting 
  one 
  group. 
  

  

  (2) 
  It 
  has 
  been 
  demonstrated 
  for 
  the 
  first 
  time 
  in 
  this 
  communication 
  

   that 
  hydrogen, 
  nascent 
  during 
  the 
  fermentation, 
  does 
  take 
  part 
  in 
  the 
  

   production 
  of 
  alcohol. 
  This 
  has 
  been 
  shown 
  to 
  be 
  true, 
  not 
  only 
  for 
  the 
  

   hydrogen 
  which 
  arises 
  from 
  the 
  decomposition 
  of 
  the 
  glucose 
  itself, 
  but 
  also 
  

   when 
  hydrogen 
  is 
  supplied 
  in 
  the 
  nascent 
  condition 
  by 
  the 
  simultaneous 
  

   fermentation 
  of 
  formic 
  acid 
  added 
  to 
  the 
  system 
  in 
  the 
  form 
  of 
  calcium 
  

   formate. 
  Such 
  a 
  proof 
  has 
  never 
  been 
  obtained 
  before, 
  either 
  for 
  bacterial 
  

   or 
  for 
  yeast 
  fermentation. 
  In 
  the 
  case 
  of 
  alcoholic 
  fermentation 
  by 
  yeast, 
  

   although 
  the 
  vague 
  expression 
  intramolecular 
  hydrogen 
  was 
  employed 
  to 
  

   indicate 
  the 
  idea 
  of 
  the 
  participation 
  of 
  hydrogen 
  in 
  the 
  formation 
  of 
  

   alcohol, 
  the 
  idea 
  was 
  not 
  substantiated 
  by 
  any 
  facts. 
  More 
  recently, 
  some 
  

   indirect 
  evidence 
  has 
  been 
  obtained 
  by 
  Neuberg 
  that 
  alcohol 
  may 
  be 
  

   produced 
  by 
  the 
  reduction 
  bv 
  yeast 
  of 
  added 
  acetaldehyde, 
  but 
  there 
  is 
  

   an 
  absence 
  of 
  any 
  direct 
  proof 
  that 
  it 
  is 
  hydrogen 
  itself 
  which 
  effects 
  this 
  

   reduction. 
  Indeed, 
  in 
  the 
  case 
  of 
  yeast 
  fermentation, 
  it 
  is 
  difficult 
  to 
  see 
  

   how 
  the 
  participation 
  of 
  hydrogen 
  in 
  the 
  process 
  could 
  be 
  demonstrated, 
  

   since 
  the 
  whole 
  of 
  the 
  hydrogen 
  of 
  the 
  sugar 
  appears 
  bound 
  up 
  in 
  the 
  final 
  

   products 
  of 
  the 
  reaction, 
  whether 
  these 
  are 
  alcohol, 
  aldehyde, 
  or 
  glycerine. 
  

   On 
  the 
  other 
  hand, 
  fermentation 
  by 
  means 
  of 
  Bacterium 
  coli 
  is 
  admirably 
  

   adapted 
  to 
  settle 
  the 
  question, 
  for 
  hydrogen 
  is 
  evolved 
  during 
  the 
  fermenta- 
  

   tion, 
  and 
  this 
  evolved 
  hydrogen 
  acts 
  as 
  a 
  gauge 
  of 
  the 
  amount 
  of 
  hydrogen 
  

   which 
  has 
  been 
  absorbed 
  in 
  the 
  formation 
  of 
  alcohol. 
  

  

  (3) 
  In 
  the 
  fermentation 
  of 
  glucose 
  by 
  B. 
  coli 
  communis, 
  it 
  has 
  been 
  shown 
  

   that 
  the 
  effect 
  of 
  the 
  presence 
  of 
  calcium 
  formate 
  is 
  peculiar. 
  

  

  If 
  carbon 
  dioxide 
  and 
  hydrogen 
  arise 
  in 
  the 
  fermentation 
  of 
  glucose 
  

   through 
  the 
  intermediate 
  formation 
  of 
  formic 
  acid 
  between 
  glucose 
  and 
  

   these 
  products, 
  as 
  has 
  hitherto 
  been 
  thought, 
  then 
  it 
  is 
  to 
  be 
  expected 
  that 
  

   the 
  addition 
  of 
  formic 
  acid 
  to 
  the 
  system 
  would 
  tend 
  to 
  depress 
  the 
  

   formation 
  of 
  that 
  substance, 
  and 
  consequently 
  lead 
  to 
  a 
  diminished 
  yield 
  

   of 
  its 
  gaseous 
  products, 
  carbon 
  dioxide 
  and 
  hydrogen. 
  In 
  these 
  experiments, 
  

   however, 
  the 
  opposite 
  has 
  occurred. 
  This 
  seems 
  to 
  mean 
  that 
  either 
  the 
  

   action 
  of 
  calcium 
  formate 
  has 
  been, 
  by 
  virtue 
  of 
  properties 
  independent 
  of 
  

   the 
  formic 
  acid 
  to 
  which 
  it 
  gives 
  rise, 
  or 
  else 
  carbon 
  dioxide 
  and 
  hydrogen 
  do 
  

   not 
  normally 
  arise 
  by 
  the 
  decomposition 
  of 
  preformed 
  formic 
  acid. 
  The 
  

  

  