120  New  Theory  of  Fermentation.        \  %^ 
of  10  flasks  each.  Those  of  the  first  series  contained  nothing  but  the 
above-mentioned  easily  fermentescible  liquid  ;  the  bulbs  in  the  second 
series  hadjadded  to  this  fermentescible  liquid  a  few  drops  of  must  or 
grape  juice,  taken  from  the  interior  of  the  grape  in  such  a  manner  as 
riot  to  come  into  contact  with  the  dust  on  the  outside  of  the  grape.  To 
the  fermentescible  liquid  in  the  bulbs  of  the  third  series  was  added  a 
small  quantity  of  the  water  in  which  the  grapes  and  stems  had  been 
washed  and  afterwards  boiled.  To  the  liquid  in  three  of  the  fourth 
series  was  added  some  of  the  water  used  to  wash  the  grape,  and  which 
contained  the  dust  and  germs,  but  had  not  been  boiled.  When  these 
preparations  were  completed,  the  bulbs  were  left  to  themselves  and  to 
the  action  of  the  surrounding  air,  in  a  room  of  a  suitable  tempera- 
ture, or  in  a  bath  artificially  heated  to  the  temperature  most  favora- 
ble to  fermentation. 
The  result  is  very  surprising,  for  it  was  found  that  the  liquid  in  the 
first  three  series,  with  rare  exceptions,  had  not  undergone  fermenta- 
tion ;  but  in  the  10  bulbs  of  the  fourth  series  a  very  violent  fermenta- 
tion had  taken  place. 
To  Pasteur  belongs  the  uncontested  honor  of  being  the  first  to  dis- 
cover that  the  organisms,  in  nature,  are  divided  into  two  classes  : 
The  first  class  consists  of  germs  visible  to  the  naked  eye,  and  in 
order  to  live  they  require  oxygen  either  free  or  combined. 
The  second  class  embraces  microscopic  organisms,  such  as  germs  of 
ferment ;  oxygen  acts  as  a  poison  on  these,  but  becomes  a  source  of 
life  if  derived  from  a  compound  like  carbonic  acid. 
It  has  long  been  a  well-known  fact  that,  in  fruits  taken  from  the 
tree  and  exposed  to  the  air,  the  vital  process  goes  on  in  the  ordinary 
manner ;  they  absorb  oxygen  from  the  surrounding  air  and  give  off 
carbonic  acid.  They  ripen  because  the  saccharine  matter  is  produced 
in  them  without  undergoing  fermentation. 
This  premise  being  established,  Pasteur  took  some  fruit,  namely,  a 
peach  and  a  plum,  and  placed  them  under  a  bell  jar  containing  car- 
bonic acid ;  the  fruit  lost  its  vitality — its  whole  life,  outer  and  inner, 
ceased,  because  it  could  not  take  up  and  assimilate  oxygen  from  the 
atmosphere  surrounding  it.  The  fruit  began  another  and  a  new  life, 
which  developed  itself  outward  from  the  interior,  and  is,  so  to  speak, 
similar  to  the  life  of  the  atoms,  in  the  sense  that  the  cellular  tissue 
takes  away  the  necessary  oxygen  from  the  saccharine  matter  and 
other  substances  present,  in  the  manner  of  a  perfect  alcoholic  fermen- 
