ACTIVE  PRINCIPLE  OF  RHUS  TOXICODENDRON. 
5 
The  Association  being  desirous  to  know  by  what  method  the 
activity  of  these  leaves  can  best  be  preserved,  I  accepted  the 
question,  and  commenced  my  experiments  in  1864,  basing  them 
upon  the  results  obtained  by  the  author  before  mentioned.  I 
may  state  here,  that  I  have  frequently  collected  the  leaves, 
flowers,  and  fruit  of  Rhus  Toxicodendron,  and  its  variety, 
radicans,  without  ever  experiencing  any  ill  effects.  I  have 
handled  all  parts  of  the  plant  with  perfect  impunity,  and  have 
even  spread  the  juice  over  my  hands,  without  feeling  more 
than  a  slight  itching  upon  the  upper  side  of  the  hand,  which 
immediately  disappeared  on  washing  the  hands  with  water. 
In  a  word,  I  considered  myself  so  little  subject  to  its  influence, 
that  I  collected  the  leaves  for  all  the  following,  experiments 
myself ;  and  on  one  occasion,  on  the  hills  of  the  Wissahickon, 
laid  down  in  the  midst  of  a  beautiful  specimen  of  Rhus  Toxi- 
codendron var.  radicans,  which  spread  so  prolificacy  over 
shrubs  and  trees,  and  through  the  grass  beneath,  that  I  was  on 
all  sides  surrounded  by  its  branches,  leaves,  and  flowers ;  al- 
though remaining  in  this  position  for  over  fifteen  minutes, 
selecting  the  most  vigorous  leaves,  I  escaped  with  no  other 
effects  than  those  described  before,  which  yielded  at  once  to 
ablutions  with  the  water  of  this  little  stream. 
I  could  hardly  expect  to  try  the  efficacy  of  the  poisonous 
principle,  when  isolated,  upon  my  own  person ;  the  result, 
however,  proved  to  be  very  different. 
But  to  return  to  the  experiments :  I  immersed  8-f  ounces  of 
the  leaves  of  the  true  Rhus  Toxicodendron  in  alcohol  in  suffi- 
cient quantity  to  cover  it,  and  added  enough  sulphuric  acid  to 
produce  a  strong  acid  reaction,  in  order  to  combine  all  the 
alkaloid.  The  vessel  was  set  aside  for  about  nine  months,  the 
alcohol  then  spontaneously  evaporated,  the  residue  forcibly 
expressed,  mixed  with  a  little  water,  and  again  expressed,  and 
the  united  liquids  distilled  with  an  excess  of  lime.  I  selected 
this  base,  because  from  its  sparing  solubility,  it  might.be  ex- 
pected to  act  less  energetically  in  inducing  decomposition  than 
potassa.  The  alkaline  distillate,  when  collected  by  itself,  re- 
minded forcibly  of  the  odor  generated  by  decoctions  of  hem- 
lock and  henbane.    The  alkali  was  collected  in  an  excess  of 
