Am.  Jour.  Pliarm.  "I 
Nov.,  1885.  i 
Action  of  Papain. 
571 
Whether  the  ferment  may  be  separated  from  the  hemialbumose  I 
am,  at  present^  unable  to  state.  Ptyalin  (Cohnheim)  and  pepsin 
(Briicke)  have  been  separated  free  from  proteid.  Trypsin,  however, 
has  not,  though  Schiitzenberger  states  that  probably  all  diastatic  and 
proteolytic  ferments  may  be  separated  from  the  accompanying  proteids. 
I  have  repeated  the  experiments  on  animal  albumen  detailed  in  my 
first  paper,  and  can  only  confirm  what  I  have  there  stated,  namely, 
that  papain  acts  like  trypsin  (though  not  so  rapidly)  in  forming  from 
coagulated  albumen  and  fibrin  a  true  peptone,  an  intermediate  body 
related  to  globulin,  and  leucin  and  tyrosin. 
I  have  extended  my  experiments  to  the  investigation  of  the  action 
of  the  ferment  on  milk,  and  on  the  proteids  found  in  papaw  juice. 
Action  on  Milk. — Papain  acts  like  pancreatic  juice  on  milk,  and  the 
experiments  I  shall  describe  are  almost  similar  to  those  performed  by 
Dr.  W.  Roberts,  of  Manchester,  with  pancreatic  extract.  Papain,  like 
pacreatic  extract,  first  curdles  the  milk,  and,  within  certain  limits  of 
temperature,  the  curds  are  more  quickly  formed  and  are  larger  the 
higher  the  temperature  up  to  62°C.  (about  145°r.),  at  which  point  the 
curdling  is  practically  instantaneous ;  for  example,  with  5  -grains  of 
papain,  and  450  cc.  of  milk,  and  125  cc.  of  water  at  62°C. 
The  curdling  is  hindered  by  making  the  milk  alkaline  with  bicar- 
bonate of  soda,  by  diluting  it,  and  also,  to  some  extent,  by  boiling  the 
milk  previously  to  the  addition  of  an  equal  quantity  of  cold  water ; 
when,  if  papain  be  added,  the  curdling  is  not  so  great,  nor  the  curds 
so  large,  as  when  the  water  is  boiled  and  added  to  the  milk.  The 
curds  in  papainized  milk  gradually  dissolve,  the  casein  being 
changed  into  peptones,  leucin  and  tyrosin  being  produced,  and  the 
liquid  becoming  bitter  to  the  taste.  Moreover,  between  the  stage  of 
casein  and  peptone  there  is  a  body  formed,  which  is  precipitated  by 
boiling  and  by  nitric  acid,  an  intermediate  body  similar  to  the  one 
developed  during  the  digestion  of  coagulated  egg  albumen.  Its  pro- 
perties were  tested  as  follows :  Seeing  that  it  must  be  formed  from  the 
curds  first  precipitated  by  the  ferment,  these  were  separated  in  one 
experiment,  and  extracted  with  a  10  per  cent,  sodium  chloride  solu- 
tion, and  the  mixture  filtered.  The  clear  filtrate  gave  a  fine  precipi- 
tate on  boiling,  and  on  adding  nitric  acid ;  and,  moreover,  a  fairly 
copious  one  on  saturation  with  sodium  chloride.  This  last  precipitate 
was  collected  and  dissolved  in  water  (by  aid  of  the  salt  present),  and 
gave  the  following  reactions,  in  addition  to  those  previously  obtained 
