168 
ON  THE  ORIGIN  OF  FERMENTS. 
to  contact  with  the  oxygen  of  the  air,  the  albuminous  element 
is  altered  and  acts  as  a  ferment.  This  ferment  reacts  upon  the 
sugar  of  the  milk,  and  transforms  it  into  lactic  acid,  which  then 
precipitates  the  casein.  This  is  the  cause  of  the  coagulation. 
In  reality^  however,  things  are  quite  otherwise.  For  if  one  of 
these  flasks  in  which  the  milk  is  coagulated  be  opened,  it  is 
obvious,  on  the  one  hand,  that  the  milk  is  as  alkaline  as  fresh 
milk;  and  on  the  other — a  circumstance  tending  to  encourage 
the  belief  in  spontaneous  generation — that  the  milk  is  filled 
with  Infusoria,  most  frequently  with  Vibrios,  as  much  as  ith 
millimeter  in  length.  As  yet  I  have  not  met  with  any  vegetable 
production  under  these  circumstances. 
From  these  facts  we  must  admit — First,  that  the  phenomenon 
of  the  coagulation  of  milk,  as  I  hope  shortly  to  demonstrate 
more  clearly,  is  a  phenomenon  upon  which  we  have  had  but 
very  imperfect  notions.  Second,  that  Vibrios  may  arise  in  a 
liquid  of  the  nature  of  milk  which  has  undergone  ebullition  for 
several  minutes  at  a  temperature  of  100*^  C,  although  this  is 
not  the  case  with  respect  to  urine,  nor  to  a  mixture  of  sugar, 
water  and  albumen.  Is  it  the  case,  then,  that  under  particular 
conditions  we  may  have  spontaneous  generation  ?  We  shall 
soon  see  how  far  this  conclusion  would  be  erroneous.  Let  the 
milk  be  boiled,  not  for  two,  but  for  three,  four,  or  five  minutes, 
and  it  will  be  found  that  the  number  of  flasks  in  which  it  coagu- 
lates from  the  presence  of  Infusoria  diminishes  progressively  in 
proportion  to  the  longer  duration  of  the  ebullition.  And  lastly, 
if  the  ebullition  be  carried  on  at  a  temperature  of  110  to  112 
degrees,  under  the  pressure  of  Ij  atmosphere,  the  milk  will 
never  aiford  any  Infusoria.  Consequently,  as  they  do  arise 
under  the  conditions  existing  in  the  former  experiments,  this  is 
evidently  due  to  the  circumstance  that  the  fecundity  of  the 
germs  of  the  Vibrios  is  not  entirely  destroyed,  even  in  water  at 
a  temperature  of  100®,  kept  up  for  some  minutes,  and  that  it  is 
more  affected  by  a  longer  ebullition  at  that  temperature,  and 
wholly  abolished  at  the  temperature  of  110*^  to  112®  C. 
But  what  is  to  be  said  concerning  the  phenomenon  of  the 
coagulation  under  those  special  conditions  of  ebullition,  in 
which  the  milk  in  contact  with  calcined  air  never  affords  any 
Infusoria  ?    One  remarkable  fact  is,  that  the  milk  does  not 
