342 
Story  of  the  Pap  aw. 
Am.  Jour.  Pharm. 
July,  1901. 
volatile  resin ;  a  substance  of  the  nature  of  fatty  acids  ;  pectose 
compounds.14 
WATER  SOLUBLE  CONTENTS. 
The  dried  latex  extracted  by  repeated  washings  with  water  gives 
8274  per  cent,  of  matter,  soluble  to  a  clear  greenish-yellow  solu- 
tion. This  watery  extract  is  of  acid  reaction  and  responds  to  the 
usual  tests  for  the  presence  of  proteids,  such  as  Millon's  rea- 
gent; the  xanthoproteic  and  biuret  tests,  etc.;  precipitates  are 
formed  by  alcohol,  tannin,  picric  acid,  platinum  chloride,  metaphos- 
phoric  acid,  lead  acetate,  Mayer's  reagent,  mercury  bichloride, 
potassium  ferrocyanid  and  acetic  acid.  The  presence  of  several 
forms  of  proteid  substances  is  also  shown  by  the  following  : 
The  filtered  solution  (noted  above)  is  rendered  turbid  by  heating 
to  the  boiling  point.  Upon  continued  boiling  a  very  fine  precipitate 
is  separated,  though  this  is  not  abundant.  Filtering  and  further 
boiling  produces  no  further  precipitation,  but  the  addition  of  nitric 
acid  drop  by  drop  gives  a  heavy  flocculent  precipitate.  The  clear 
aqueous  extraction  noted  above,  slightly  acidulated  with  hydro- 
chloric acid  and  heated,  shows  a  slight  turbidity  just  before  reaching 
the  boiling  point.  Cooling  and  the  further  addition  of  the  acid 
produces  at  once  a  heavy  flocculent  precipitate,  which  dissolves 
upon  heating  and  reappears  upon  cooling. 
A  solution  of  sodium  carbonate  (0-5  per  cent.)  added  to  the  clear 
aqueous  extract  of  the  dried  latex  produces  an  immediate  turbidity 
which,  upon  heating,  separates  into  a  small  amount  of  fine  precipi- 
tate. From  these  last  results  it  will  be  seen  that  the  soluble  albu- 
mins of  the  latex  of  the  papaw  are  only  partially  coagulated  by 
heat. 
When  concentrated  hydrochloric  acid  is  cautiously  added  to  the 
clear  watery  extract  of  the  latex,  there  is  formed  a  heavy  curdy 
precipitate,  soluble  in  an  excess  of  the  acid.  In  a  clear  aqueous 
solution  of  the  latex,  concentrated  nitric  acid  pioduces  a  heavy 
14  Malic  acid  has  been  noted  as  being  present  in  the  latex  of  the  papaw.  The 
acid  principles  of  these  extracts  of  the  milk  when  subjected  to  the  usual  tests 
for  malic  acid,  gave  but  slight  indications  of  its  presence. 
The  aqueous  solution  of  the  latex  was  examined  at  length  and  judging  by 
the  reactions  noted  in  the  text-books,  and  compared  with  malic  acid  itself, 
the  conclusion  was  reached  that  no  malic  acid  or  malates  were  present. 
