270  Use  of  Copper  in  Destroying  Typhoid.  {Amj^ne!"i£5arm" 
placed  in  soil  containing  1  part  or  even  more  of  copper  sulphate  in 
2,000  parts  of  soil  they  remain  uninjured. 
Nageli's1  experiments,  performed  during  the  '8o's,  showed  that 
certain  unicellular  plants,  as  the  algae,  were  killed  by  solutions  con- 
taining exceedingly  minute  quantities  of  copper.  His  experiments 
have  been  repeatedly  confirmed,  and  Israel  and  Klingmann  observed 
a  similar  toxic  action  on  other  unicellular  plants,  notably  some  of 
the  fecal  bacteria  and  also  on  some  of  the  unicellular  animal 
organisms. 
While  there  are  these  experiments  showing  that  certain  plants 
and  animals  are  killed  by  solutions  containing  as  little  as  1  part  of 
copper  to  1,000,000,000  of  water,  still  there  are  other  plants  which 
are  stimulated  and  under  certain  conditions  even  appear  to  be  bene- 
fited by  its  presence.  Frank  and  Krueger2  have  shown  that  if  potato 
plants  are  properly  supplied  with  copper,  the  plants  are  hardier, 
yield  a  larger  crop,  and  live  longer  than  they  otherwise  would. 
We  may  say  in  a  general  way  that  there  are  certain  organisms 
which  manifest  a  specific  sensitiveness  towards  copper,  including 
bacteria,  one  of  the  annelid  worms,  as  well  as  other  human  para- 
sites, while  others  are  unaffected  or  even  stimulated  by  relatively 
large  quantities  of  copper  sulphate.  The  unicellular  organisms  are 
the  ones  which  appear  to  be  most  sensitive  to  the  action  of  copper. 
THE  EFFECTS  OF  WATER  TREATED  WITH  COPPER  ON  MAN. 
While  it  has  been  conclusively  shown  that  exceedingly  minute 
quantities  of  copper  are  toxic  to  typhoid  organisms,  still  the  ques- 
tion is  raised  by  some  as  to  the  toxic  effects  on  man  when  copper 
or  its  salts  is  used  in  the  purification  of  drinking-water.  In  com- 
menting on  a  paper  of  mine  on  "  The  Efficiency  of  Copper  Foil  in 
Destroying  Typhoid  and  Colon  Bacilli  in  Water,"  a  reviewer3  writes 
as  follows :  "  While  recommending  the  use  of  copper  foil  for  the 
purification  of  drinking-water,  the  writer  adduces  no  proofs  as  to 
freedom  from  toxic  effects  when  water  so  purified  is  taken  into  the 
system  over  a  considerable  period  of  time."  My  reason  for  not  taking 
1  Ueber  oligodynamische  Erscheinungen  in  lebenden  Zellen.  Neue  Denk- 
schriften  der  schweizerischen  naturforschenden  Gesellschaft,  33-34  (1893- 
1895). 
2  Ber.  d.  Deutsch.  Bot.  Ges.,  12,  1894,  p.  8. 
3  Medical  Notes  and  Queries,  1,  No.  3,  March,  1905,  p.  38. 
