480 
Acid  Fermentation  of  Milk. 
( Am.  Jour.  Pharm. 
I      Sept.,  1889. 
very  subsidiary  one.  For  his  experiments  he  first  takes  four  small 
retorts  (Kolbchen)  containing  each  50  ccm.  of  sterilized  milk,  and  adds 
to  them  different  quantities  of  a  pure  culture  of  the  so-called  milk 
ferment  germ,  e.  g. : — 
Pure  culture  Acidity  after 
Vessels.  germs.  One  day.  Two  days. 
1    1  drop    28-4   42'5 
2    2   "    285    42-4 
3    10   "    289    43-5 
4    50   "    302    43'5 
This  experiment  was  repeated  several  times,  always  with  a  similar 
result.  The  natural  conclusion  is  that  the  fermentation  is  influenced 
by  something  besides  the  germs.  Might  it  be  the  casein  ?  Before 
Pasteur  discovered  the  germs  Liebig  held  that  casein  was  the  specific 
milk  ferment,  and  the  following  experiment  supports  Liebig : — 
Casein  prepared  Acidity  afcer 
and  filtered.  1  day.  2  days. 
1    66    10-9 
2    6*6    11-0 
3    6'8    11-3 
Not  filtered. 
1    31    06 
2    33    T4 
3    3*3    1-7 
The  next  experiment  with  casein  added  is  still  more  striking  : — 
Casein  Acidity  after 
added.  1  day.  2  days. 
1    0    27    5*7 
2    1  ccm   4-0    9-3 
3    5   «   76    12*3 
4    10   "   !         107    197 
This  proves  that  the  amount  of  casein  has  considerable  influence ; 
still,  the  fermentation  is  not  in  proportion  to  the  amounts  of  casein 
added.  This,  however,  is  explained  by  the  increased  concentration 
of  the  fluid,  as  a  parallel  experiment,  with  fresh  milk  (infected  with 
sour)  and  milk  sugar,  proves : — 
Milk  sugar  Acidity  after 
solution.  1  day.  2  days- 
1    0    3*8    4*0 
2    5  ccm   4*5   5*4 
3    10   «    50    7-3 
4    20   "    6'5    2-1 
