390 
Story  of  the  Pap  aw. 
(Am.  Jour.  Pharm. 
\      August,  1901. 
characteristics ;  whereas,  the  ferments  of  the  papaw  can  be  mixed 
with  other  ferments  in  a  solution  of  any  reaction.  Pepsin  is  inert 
in  a  neutral  solution,  and  is  destroyed  in  solutions  containing  traces 
of  alkalinity.  If  an  alkaline  solution  of  pepsin  be  made  acid,  the 
pepsin  action  is  not  restored ;  pancreatin  acts  slowly  in  neutral 
solutions,  and  is  destroyed  in  acid  solution.  If  an  acid  solution  of 
pancreatin  be  made  alkaline,  the  pancreatin  action  will  not  be  re- 
stored. The  papaw  ferments  are  active  in  neutral  solutions  ;  their 
activity  is  enhanced  when  such  solution  is  made  acid,  and  if  such 
acid  solution  be  in  turn  made  alkaline,  the  ferment  will  still  remain 
active.  In  fact,  the  changing  of  solution  of  the  papaw  ferments 
from  acid  to  neutral,  then  to  alkaline;  then  reversing  the  order  to 
neutral,  acid  and  alkaline,  or,  in  fact,  changing  the  order  of  reaction 
almost  indefinitely,  does  not  thereby  destroy  the  ferment  which 
seems  to  remain  active  under  all  reactions  and  conditions. 
Certain  physical  changes  in  the  proteid  substances  acted  upon 
are  characteristic  of  these  enzymes  of  the  papaw.  For  instance : 
when  raw  blood  fibrin  or  raw  beef  is  acted  upon  with  an  alkaline 
solution  of  these  ferments,  there  is  an  immediate  softening  to  a 
jelly-like  mass  in  which  the  fibres  lose  their  individuality,  this  jelly 
gradually  becoming  thinner  under  the  further  action  of  the  ferment.20 
In  the  case  of  cooked  beef  in  either  alkaline  or  acid  solution,  the 
action  of  the  ferment  of  the  papaw  is  quite  different.  There  is  a 
rapid  disintegration  of  the  fibres  which  separate  into  tiny  fragments. 
Finally  the  undigested  portion  becomes  a  pultaceous  residue.21 
A  most  interesting  feature  of  the  papaw  enzyme  is  its  action  at  a 
wide  range  of  temperature.  With  the  animal  ferments,  especially 
pepsin  and  trypsin,  digestion  is  very  slow  at  room  temperature,  68 
to  70  F.  While  at  this  temperature  the  papaw  enzyme  acts  as 
energetically  as  at  1 10  F.,  the  animal  ferments  act  most  energetic- 
ally at  body  temperature  (diastase  at  130  F.) 
20  This  action  in  the  case  of  blood  fibrin  is  quite  striking,  and  advantage  is 
taken  of  this  property  in  therapeutics  where  a  solution  of  the  ferments  is  used 
as  a  solvent  for  the  false  membrane  of  diphtheria,  a  substance  quite  analogous 
to  blood  fibrin. 
21  It  is  notable  that  with  meat  proteids,  both  cooked  and  uncooked,  in  acid 
or  alkaline  solutions  containing  no  ferment,  there  is  a  marked  swelling  of  the 
fibre.  In  an  alkaline  solution  this  becomes  a  solid  jelly,  but  this  swelling 
seems  to  be  entirely  counteracted  by  the  presence  of  the  papaw  ferment. 
