Am.  Jour.  Pharm.) 
November,  1907.  / 
Poison  Sumac. 
501 
In  1865  J.  M.  Maisch1"  denied  the  presence  of  a  volatile  alkaloid 
in  poison  ivy,  but  announced  the  discovery  of  a  new  volatile  acid  to 
which  he  ascribed  the  poisonous  properties  of  that  plant,  and  to 
which  he  gave  the  name  "  toxicodendric  acidy  He  prepared  salts 
of  this  acid,  and  stated  that  its  properties  were  somewhat  similar  to 
those  of  formic  acid  and  acetic  acid,  but  more  nearly  like  the  latter 
The  conclusions  of  Professor  Maisch  remained  unverified  for  thirty 
years,  and  standard  works  on  pharmacology  quoted  them  without 
question  until  Dr.  Pfaff  investigated  the  subject  in  1894-96. 
Dr.  Pfaff11  proved  that  the  "toxicodendric  acid"  of  Maisch  was 
acetic  acid,  and  that  the  real  poison  of  ivy  (and  sumac)  existed  in 
an  oily  substance  which  he  named  "  toxicodendron"  and  which 
was  completely  non-volatile. 
He  states  that  he  prepared  this  oil12  by  repeated  fractional  pre- 
cipitations of  its  lead  salt  from  alcoholic  solution  by  means  of 
alcoholic  solution  of  lead  acetate.  The  free  oil  was  obtained  from 
its  lead  compound  by  decomposing  the  latter  with  ammonium 
sulphide.  He  found  the  poisonous  oil  in  all  parts  of  the  plant — 
stems,  branches,  roots,  leaves  and  fruit.  It  was  present  in  both  ivy 
and  sumac,  but  more  abundant  in  the  latter.  Dr.  Pfaff  does  not 
state  whether  the  "  toxicodendrol "  was  obtained  from  the  green  or 
the  ripened  fruit,  an  omission  to  which  we  will  again  refer.  Accord, 
ing  to  this  author,  "  toxicodendrol  "  is  soluble  in  ether,  alcohol, 
chloroform  and  similar  solvents,  but  is  insoluble  in  water. 
It  is  easily  decomposed  by  heat  and  is  partially  converted  into 
resin  on  long  standing.  None  of  its  other  physical  or  chemical 
properties  or  constants  were  determined.  The  fruit  of  Rhus  toxico- 
dendron contained  3-6  per  cent,  of  crude  oil  (i.  e.,  active  oil  con- 
taminated with  resinous  matter  and  with  oil  not  precipitated  by  lead 
acetate),  the  leaves  3-3  per  cent,  and  the  stems  and  branches  i-6per 
cent; 
Rhus  vernicifera,  the  Japanese  varnish  tree,  exhibits  poisonous 
properties  similar  to  the  American  sumac.  The  milk  juice,  which 
exudes  when  the  plant  is  wounded,  forms  the  Japanese  lac  ot 
Oriental  commerce.    Several  chemists  have  investigated  the  prop- 
10  Proc.  Am.  Pharm.  Assoc.,  1865,  166. 
11  J.  Exp.  Med.,  Vol.  II,  No.  2,  1897. 
12  J.  Exp.  Med.,  Vol.  II,  No.  2  (1897),  187. 
