178 
Enzymes  of  Cozv's  Milk. 
fAm.  Jour.  Pharm. 
\       April,  1909. 
number  of  times.  Thus,  invertase  is  capable  of  inverting  at  least 
200,000  times  its  own  weight  of  cane  sugar  {Jour.  Chem.  Soc. 
Trans.,  57,  384,  1890),  and  rennin  at  least  400,000  parts  of  casein. 
The  action  of  the  ferments  should  be,  theoretically,  an  unlimited  one. 
There  is,  however,  as  has  been  shown  in  the  case  of  rennin  (Reichel 
and  Spiro:  Hofmeister's  Beitrage  6,  68,  1904,  and  7,  479,  1905) 
a  gradual  loss  of  efficiency.  This  is  not,  however,  caused  by  the 
reaction  of  itself,  but  by  other  factors. 
Now,  as  to  the  specific  ferments  of  milks :  The  most  important 
of  these  is  galactose,  a  proteolytic  enzyme  of  the  tryptic  group,  dis- 
covered by  Babcock  and  Russell  in  1897.  These  investigators  ob- 
served that  milk  kept  under  certain  antiseptic  conditions  showed,  in 
time,  a  progressive  increase  in  the  percentage  of  "  nitrogen  com- 
pounds soluble  in  water,"  which  were  formed  at  the  expense  of 
the  casein. 
"  In  milk  12  days  old  ('  The  Soluble  Ferments,'  by  J.  Reynolds 
Green,  1901,  207),  the  nitrogen  existing  in  this  condition  was  30 
per  cent,  of  the  total  nitrogen ;  in  one  240  clays  old,  it  had  become 
63  per  cent.  In  another  sample,  twelve  hours  after  milking,  it  was 
less  than  10  per  cent.,  but  after  three  weeks'  standing  it  had  risen 
to  30  per  cent.  During  all  this  time  bacteria  were  found  to  be 
entirely  absent.  These  changes  in  milk  did  not  take  place  in  samples 
that  had  been  boiled  at  the  outset." 
These  experiments  clearly  demonstrated  the  presence  of  a 
proteolytic  ferment  in  fresh  milk.  The  ferment  was  isolated  by 
centrifuging  the  milk,  collecting  the  slime  that  remained  adhering  to 
the  instrument,  mixing  it  with  an  equal  weight  of  40  per  cent, 
alcohol,  and  adding  an  antiseptic.  After  standing  twenty-four  hours, 
the  mixture  was  filtered,  the  filtrate  concentrated  by  evaporation  at 
52°  C.  to  one-tenth  its  original  volume,  additional  antiseptic  being 
added.  The  faintly  acid  solution  was  then  neutralized  with  sodium 
carbonate,  when  syntonin  and  calcium  phosphate  were  precipitated. 
The  filtrate  from  this  precipitate  curdled  milk,  and  subsequently 
dissolved  the  curd,  indicating  the  presence  of  rennet  and  a  proteolytic 
ferment. 
While  galactase  belongs  to  the  tryptic  group,  it  differs  from 
trypsin  in  forming  not  only  amido-acids,  and  albumoses  and  pep- 
tones/but  later,  also,  a  certain  quantity  of  ammonia. 
The  principal  properties  of  galactase  are: 
(1)  It  hydrolyzes  proteids,  especially  casein,  carrying  the  de- 
composition to  the  liberation  of  ammonia. 
