ADecSerPih9Hm'}^^aw^af^^a^ow  °f  Commercial  Papain.  543 
hydroxide,  and  that  the  fibrin  is  acted  on  for  from  four  to  five  hours 
at  450  to  500  C.  It  is  there  further  stated,  however,  that  the  products 
of  several,  different  manufacturers  vary  as  to  their  activity  in  acid 
and  alkaline  medium  respectively.  Thus  it  is  stated  that  the  prep- 
arations of  E.  Merck  and  of  Gehe  &  Co.  acted  best  in  alkaline 
medium,  while,  on  the  other  hand,  those  of  Boehringer  and  of 
Finkler  were  active  in  acid  solution. 
The  fibrin  test  has  been  little  used  in  this  country  because  of  the 
doubtfulness  of  the  method  and  because  cff  the  experimental  diffi- 
culties involved  in  carrying  it  out.  During  recent  years  our  litera- 
ture contains  several  contributions  dealing  with  assay  methods  which 
are  more  Serviceable  than  the  assay  by  means  of  fibrin. 
However,  during  the  period  in  which  these  newer  methods  were 
being  evolved  the  commercial  product  has  been  adulterated  to  a 
shameful  extent,  and  the  terms  "papain"  and  "pawpaw  juice"  are  not 
now  characteristic  of  two  different  products.  Indeed,  papain  now 
really  signifies  dried  pawpaw  juice.  We  have  found  no  products 
on  the  market  having  a  higher  digestive  strength  than  has  dried 
pawpaw  juice,  although  the  terms  "papain,"  "purified  papain,"  "con- 
centrated active  principle,"  etc.,  were  used  in  describing  some  of  the 
various  products.  Some  of  these  were  offered  for  greatly  advanced 
prices,  in  one  case  the  price  per  pound  being  almost  $10.  Official 
recognition  of  this  product,  as  well  as  a  method  for  standardization, 
is  very  desirable. 
Among  the  newer  methods,  we  have  one  described  by  Graber.2 
This  method  is  that  of  allowing  10  grammes  of  properly  prepared 
round  steak  to  stand  with  0.325  gramme  of  papain  in  the  presence  of 
85  c.c.  of  0.3  per  cent,  hydrochloric  acid  at  520  C.  for  six  hours-. 
The  undigested  portion  should  not  measure  more  than  2  c.c.  in  a 
graduated  settling  tube.  The  proteolytic  activity  then,  under  these 
conditions,  is  I  > :  30.  Graber  describes  the  results  obtained  by  this 
method  in  studying  the  activity  of  pawpaw  juice,  but  not  of  com- 
mercial papain.  He  found  the  proteolytic  activity  on  steak  to  be 
greatest  in  a  0.3  per  cent,  hydrochloric  acid  medium. 
Horace  North  3  examined  twelve  samples  of  commercial  papain, 
six  of  which  proved  by  his  method  to  be  inactive.  The  experimental 
values  showing  the  comparative  activity  of  the  six  genuine  samples 
2  Jour.  Ind.  and  Eng.  Chem.}  3,  919  (1911). 
6  Report  of  Lehn  &  Fink's  Analytical  Department,  1910-1912,  p.  66. 
