528  Poisonous  Nature  of  Jatropha  Urens.  {^viS/mF' 
The  stinging  hairs  of  Jatropha  urens  show  the  same  structure 
as  those  of  the  common  nettle  ( Urticacese ) ,  though  the  two  plants 
belong  to  different  families.  The  poison  is  produced  by  a  cell  of  the 
epidermis  which,  during  the  growth,  swells  up,  forming  a  goblet- 
shaped  bulb,  set  into  the  surrounding  tissue.  The  hair  then  represents 
a  long  tube,  the  walls  of  which  have  incrustations  of  silicic  acid  in 
the  upper  part  and  are  calcified  in  the  lower  parts,  so  that  they  are 
very  brittle  and  break  at  the  lightest  touch.  Near  the  top  this  cell 
expands  a  little,  in  the  form  of  a  miniature  hat  with  very  thin  walls, 
so  that  when  touched,  it  breaks  in  an  oblique  direction,  forming  the 
point  of  a  cannula,  which  enters  the  skin  of  animal  or  man.  At  the 
same  time  the  poisonous  liquid  of  the  cell  is  discharged  into  the 
wound,  and  produces  instantly  a  local  inflammation.  The  mechan- 
ism is,  in  fact,  the  same  as  that  of  the  poison  fang  of  the  snakes,  and 
it  is  also  similar  to  the  cannula  of  the  surgeon. 
To  estimate  the  formidable  effects  of  the  hair  and  the  intensity 
of  its  poisonous  liquids,  it  has  been  calculated  that  about  10,000  hairs 
of  the  common  nettle  may  produce  one  drop  of  poison  (0.05  c.cm.). 
As  in  the  case  I  am  going  to  mention,  about  10  hairs  of  the  Jatropha 
were  broken.  It  may  be  calculated  on  the  same  basis  that  about 
0.00005  c.cm.  of  poison  entered  the  wound.  This  is,  however,  a  low 
estimate,  because  the  hairs  of  our  plant  and  their  inner  cavity  are 
larger  than  those  of  the  common  nettle  and  the  amount  of  poison 
introduced  into  the  system  in  the  following  occurrence  was  prob- 
ably much  larger  than  it  would  have  been  in  the  case  of  an  equal 
contact  with  Urtica  urens. 
On  an  excursion  along  the  San  Felix  River,  in  eastern  Chiriqui, 
with  Dr.  MacDonald,  geologist  of  the  Canal  Commission,  the  writer 
became  acquainted  with  Jatrc  pha  urens  by  unavoidable  contact  with 
a  single  specimen  of  the  plaM.  All  at  once  he  felt  an  intense  burn- 
ing on  the  left  hand,  where  about  10  of  the  stinging  hairs  had  entered 
pretty  deep  into  the  skin.  The  inflammation  produced  by  this  touch 
was  very  similar  to  that  produced  by  nettles,  but  the  pain  soon  in- 
creased, the  whole  hand  began  to  swell  and  inside  of  half  an  hour 
had  assumed  a  monstrous  shape.  Then  the  arm  commenced  to  swell 
also,  the  right  hand  and  arm,  without  having  been  inoculated,  yet 
showed  the  same  abnormal  symptoms,  and  a  very  strong  itching 
sensation  was  felt  all  over  the  upper  part  of  the  body.  At  about 
the  same  time  parts  of  the  face,  around  the  eyes  and  nose,  swelled 
