Am.  Jour.  Pbarm. 
Sept.,  1886. 
Nature  of  Papain. 
439 
the  alkaline  phosphates  present  in  saliva.  When  the  proteid  matter 
present  is  saturated  with  acid,  the  saliva  has  greater  diastatic  power 
than  when  it  is  simply  neutralized.  Small  percentages  of  acid  peptone 
act  similarly,  but  beyond  a  certain  point  (when  the  amount  of  com- 
bined acid  is  over  0*006  per  cent.),  acid  proteids  retard  and  finally 
destroy  the  action  of  the  ferment.  A  minute  trace  of  free  acid  in 
dilute  saliva  still  further  increases  diastatic  activity,  but  0'003  per 
cent,  of  free  hydrochloric  acid  stops  it. — Jour.  Chem.  Soc,  July, 
1886,  p.  638 ;  Chem.  News,  vol.  53. 
NATURE  OF  PAPAIN  ASD  ITS  ACTION  ON  VEGETABLE 
PROTEID. 
By  S.  H.  C.  Martin. 
The  ferment  in  papaw  juice  is  associated  with  an  albumose,  and  to 
the  reactions  previously  stated  by  Wurtz,  the  following  are  added  : 
the  solution  gives  a  biuret  reaction,  and  it  is  precipitated  from  a 
neutral  solution  by  sodium  magnesium  sulphate,  the  precipitate  still 
being  active.  It  is  not  precipitated  by  magnesium  sulphate  or  sodium 
chloride  alone,  as  globulins  are.  It  is  soluble  in  glycerol,  and  if  pre- 
cipitated from  this  solution  by  alcohol  the  filtrate  has  no  proteolytic 
power.  The  kind  of  albumose  is  one  nearly  akin  to  the  protalbumose 
of  Kuhne  and  Chittenden,  and  is  called  a-phytalbumose.  Papaw 
juice  also  contains  a  milk-curdling  ferment. 
The  proteids  present  in  papaw  juice  were  found  to  be  as  follows: 
1.  Globulin,  resembling  serum  globulin  in  its  most  important  prop- 
erties. 2.  Albumin.  3.  /3-Phytalbumose  precipitated  almost  com- 
pletely by  heat,  by  saturation  with  neutral  salts,  but  not  by  dialysis. 
It  differs  from  the  heteroalbumose  of  Kuhne  and  Chittenden, 
by  not  being  precipitated  by  dialysis,  by  copper  sulphate  or  by 
mercuric  chloride.  4.  a-Phytalbumose ;  soluble  in  cold  or  boiling 
water ;  not  precipitated  by  saturation  with  neutral  salts,  except  in  an 
acid  solution.  This  is  the  vegetable  peptone  referred  to  by  Vines 
(J.  Physiol.,  iii)  as  hemialbumose.  It  differs  from  the  protalbumose  of 
Kuhne  and  Chittenden  by  its  non-precipitation  by  sodium  chloride 
or  by  copper  sulphate.  Both  these  albumoses  give  the  biuret  reaction. 
No  peptones  occur  in  the  juice,  but  leucine  and  tyrosine  are  present. 
By  a  series  of  digestion  experiments  carried  out  on  each  of  these 
proteids  by  papain  in  a  neutral  liquid,  it  was  found  that  both  the 
