^eciXSoT'}      The  Copper  Treatment  of  Water.  577 
of  micro-organisms  in  water,  we  used  solutions  having  respectively 
the  strengths  of  1  part  of  copper  sulphate  to  100,000  parts  of  water, 
and  of  1  part  of  copper  sulphate  to  1,000,000  parts  of  water;  tap 
water  was  used  after  it  was  allowed  to  run  about  five  minutes,  and 
the  solution  was  kept  at  room  temperature  for  forty-eight  hours. 
In  this  time  there  was  a  reduction  of  the  total  number  of  organisms 
in  the  first  instance  of  99  per  cent,  and  in  the  second  of  90  per  cent. 
The  experiments  which  we  are  conducting,  are  in  the  main,  how- 
ever, with  colloidal  copper,  the  reasons  for  which  need  not  be  stated. 
For  this  work  my  original  intention  was  to  use  copper  vessels ;  but 
finding  that  I  would  have  to  wait  some  time  to  have  these  made, 
those  on  the  market  being  tin-lined,  I  decided  to  use  strips  of  cop- 
per foil  instead.  The  ordinary  methods  for  the  bacteriological  ex- 
amination of  water  were  followed,  Heyden's  nutrient  agar  being  used 
so  as  to  obtain  the  growth  of  the  maximum  number  of  organisms. 
The  mode  of  preparing  this  medium  and  its  advantages  are  de- 
scribed by  Dr.  Robin  in  the  March  number  of  this  Journal.  Ordi- 
nary sheet  copper  in  thin  pieces  was  used,  these  being  about  1 5 
centimeters  square  for  each  1,000  c.c.  of  water,  and  being  cleaned 
each  time  with  a  little  powdered  pumice.  In  some  of  the  earlier 
experiments  ordinary  tap  water  was  used  (as  much  as  2,000  c.c. 
being  experimented  with),  and  it  was  found  that  from  85  to  97  per 
cent,  of  all  the  organisms  were  destroyed.  In  these  experiments,  as 
in  those  above  mentioned,  it  is  understood  that  if  any  typhoid  and 
colon  organisms  were  present,  they  would  have  been  among  the  first 
to  be  destroyed. 
The  systematic  study  of  the  organisms  which  persist  as  well  as 
those  which  were  killed,  is  being  continued,  and  will  be  reported  on 
later.  In  order  to  satisfy  myself  that  both  colon  and  typhoid  or- 
ganisms are  completely  destroyed  by  the  presence  of  copper  foil, 
another  series  of  experiments  was  made,  using  pure  cultures  of 
typhoid  and  of  colon  bacilli,  which  were  allowed  to  develop  from 
eighteen  to  twenty  four  hours  in  bouillon.  Two  3-millimeter  loops 
were  added  to  200  c.c.  of  water  under  three  different  conditions,  con- 
trol experiments  being  conducted  at  the  same  time.  These  were  as 
follows:  (1)  Filtered  tap  water,  which,  after  treatment  with  potas- 
sium permanganate,  was  distilled  two  or  three  times,  the  apparatus 
being  constructed  entirely  of  glass  ;  (2)  tap  water  which  was  filtered  ; 
and  (3)  ordinary  tap  water.    All  three  were  sterilized  in  an  auto- 
