10  ACTIVE  PRINCIPLE  OF  RHUS  TOXICODENDRON. 
That  it  is  the  principle  to  whieh  the  poison  oak  owes  its  effects 
on  the  human  system,  was  proved  to  my  entire  satisfaction  by 
the  copious  eruption  and  the  formation  of  numerous  vesicles  on 
the  back  of  my  hand,  on  the  fingers,  wrists,  and  bare  arms, 
while  I  was  distilling  and  operating  with  it.  Several  persons, 
coming  into  the  room  while  I  was  engaged  with  it,  were  more 
or  less  poisoned  by  the  vapors  diffused  in  the  room;  and  I  even 
transferred  the  poisonous  effects  to  some  other  persons,  merely 
by  shaking  hands  with  them. 
The  dilute  acid,  as  obtained  by  me,  and  stronger  solutions  of 
its  salts,  were  applied  to  several  persons,  and  eruptions  were 
produced  in  several  instances,  probably  by  the  former,  though 
not  always,  which  was  most  likely  owing  to  the  dilute  state  of 
the  acid.  Whenever  this  was  boiled,  I  always  felt  the  same 
itching  sensation  in  the  face,  and  on  the  bare  arms,  which  I 
experience  on  continual  exposure  of  my  hands  to  the  juice  of 
the  plant. 
As  remedies  against  it,  I  have  tried  subacetate  of  lead,  per- 
manganate of  potassa  and  ammonia,  the  last,  I  believe,  with 
the  best  success.  Alkaline  solutions  were  first  recommended 
by  Prof.  Procter,  I  believe,  and,  as  my  experiments  show,  they 
are  the  remedies  which,  «  priori,  might  be  expected  to  afford 
the  greatest  relief,  just  as  in  the  case  of  formic  acid.  The  erup- 
tion produced  by  this  acid  is  very  similar  in  its  nature  to  the 
one  produced  by  toxicodendric  acid,  and  its  effects  yield  readily 
to  alkaline  lotions.  It  is  not  unlikely  that,  like  the  formiates, 
the  toxicodendrates  are  without  any  ill  effects,  if  applied  ex- 
ternally. The  reactions  of  our  new  acid  show,  likewise,  the 
reason  why  permanganate  of  potassa,  subacetate  and  even 
acetate  of  lead  may  be  valuable  remedies  for  this  eruption. 
While  the  former  completely  decomposes  it,  the  last  named 
salts  produce  nearly  insoluble  precipitates  with  it ;  at  least, 
toxicodendric  appears  to  be  stronger  in  its  affinities  than  acetic 
acid. 
The  question  may  now  be  asked,  how  Dr.  Khittel,  in  his 
otherwise  carefully  performed  analysis,  could  overlook  such 
an  important  constituent  ?  The  answer  is  partly  given  in  the 
remarks  previously  made ;  the  drying  and  powdering  of  the 
