ADeceZerPS'}      The  Pollen  of  Poison  Sumach.  545 
invariably  the  same.  The  decomposition  in  those  solutions  containing 
acetanilide,  is  only  a  small  fraction  of  that  in  the  corresponding 
solutions  which  do  not  contain  the  preservative. 
There  can  be  no  question  as  to  the  usefulness  of  this  substance 
for  the  purpose.  As  to  the  mineral  impurities,  the  salts  of  the  alkali 
and  alkaline-earth  metals  and  all  other  salts  used,  except  those  of  cop- 
per and  iron,  appear  to  have  no  influence  whatever  upon  the  stability 
of  the  solutions  when  acetanilide  is  used.  Traces  of  copper  and 
iron  have  a  very  deteriorating  effect  but  this  is  prevented  to  a  great 
extent  by  acetanilide.  The  concentration  of  iron  used  was  consider- 
ably greater  than  that  which  need  be  present  in  a  commercial  solu- 
tion. Without  acetanilide,  silica  appears  to  have  a  deteriorating 
effect  but  this  result  is  almost  neutralized  by  the  preservative.  As 
previously  indicated  in  the  tables,  the  concentration  of  acids  used  in 
series  IV,  V  and  VI  was  T^y  normal,  which  is  the  maximum  limit 
allowed  by  the  U.S. P.  The  decomposition  of  the  preserved  solu- 
tions of  series  IV  (HQ)  was  more  than  twice  as  great  as  that  in  the 
case  of  the  other  two  series.  An  explanation  of  this  may  be  found 
in  the  fact  that  all  the  solutions  of  series  IV  that  contain  acetanilide, 
deposited  a  yellow  sediment  of  organic  matter  on  standing. 
It  is  of  considerable  interest  to  note  that  the  stability  of  the  pure 
peroxide  of  series  I  and  II  which  contains  acetanilide  alone,  is  about 
the  same  as  that  of  the  preserved  solutions  of  series  V  and  VI,  which 
were  acidified. 
Scientific  Laboratory  of  Parke,  Davis  &  Co., 
Detroit,  Mich.,  Oct.  27,  1913. 
SOME  OBSERVATIONS  ON  THE  POLLEN  OF  POISON 
SUMACH. 
By  L.  E.  Warren. 
From  prehistoric  times  it  has  been  known  that  contact  with  cer- 
tain plants  would  occasionally  produce  inflammatory  conditions 
in  the  skin  of  human  beings.  Until  within  comparatively  recent 
years  the  belief  has  been  quite  general  that  such  plants  as  the  poison 
ivy  and  poison  sumach,  which  are  more  venomous  than  most  others, 
give  off  an  invisible,  mysterious  emanation  or  vapor  which,  if 
allowed  to  touch  the  skin,  produces  the  complex  symptoms  so  well 
