AmjinUe^i9oh5arm'}     Use  of  Copper  in  Destroying  Typhoid,  273 
THE  OCCURRENCE  OF  COPPER  IN  FOODS. 
Among  the  other  inorganic  constituents  which  occur  normally  in 
the  animal  organism  is  copper,  and  its  occurrence  is  so  constant  as 
to  be  spoken  of  as  "  normal  copper."  It  is  not  known,  however, 
what  part,  if  any,  it  plays  in  metabolism.  The  amount  normally 
present  varies  with  the  food  and  with  the  individual.  There  is  con- 
siderable data  showing  that  the  amount  of  copper  in  vegetables 
varies  according  to  the  amount  of  copper  present  in  the  soil,  and 
owing  to  its  wide  distribution  in  soil,  it  is  found  in  many  plants. 
It  is,  therefore,  naturally  present  in  many  foods,  and  may  run  as 
high  as  0*560  gramme  per  kilogramme  of  dried  substance,  or  even 
I  part  in  1,785  parts,  in  plants  growing  near  copper  works,  as 
shown  by  Lehmann.1 
In  addition,  copper  is  added  to  many  foods  to  enhance  their  ap- 
pearance. The  custom  of  greening  vegetables  has  been  followed  in 
a  commercial  way  for  over  fifty  years,  and  laws  are  being  enacted 
defining  the  limit  of  copper  which  is  permissible  in  food  materials. 
The  Swiss  and  Italian  Governments  allow  a  quantity  of  metallic 
copper  not  to  exceed  100  milligrammes  per  kilogramme  (or  1  part 
in  10,000)  in  vegetable  preserves.  In  France  the  question  of 
re-greening  vegetables  by  means  of  copper  sulphate  has  received 
careful  attention,  and  while  the  practice  was  prohibited  by  law  in 
1853,  this  prohibitory  law  was  repealed  in  1889.  According  to 
Leach  :  "  Examination  of  a  large  number  of  brands  of  canned  vege- 
tables greened  by  copper,  as  bought  in  Massachusetts,  showed  that 
the  amount  used  varied  from  a  trace  to  2-75  grammes  per  can,  cal- 
culated as  copper  sulphate.  .  .  .  In  the  Massachusetts  market 
labels  like  the  following  are  not  uncommon :  *  This  package  of 
French  vegetables  contains  an  equivalent  of  metallic  copper  not  ex- 
ceeding ^  of  a  grain.'  "  In  Pennsylvania  the  law  "  permits  articles 
of  vegetable  food  to  contain  as  much  as  ^  of  1  per  cent,  of  metallic 
copper,"  or  I  part  to  5,000  parts  of  food. 
The  following  table  shows  the  amount  of  copper  found  in  various 
substances.  A  key  to  the  literature  quoted  is  afforded  by  the 
numbers  in  parentheses. 
1  "  Hygienische  Studieti  iiber  Kupfer  IV,"  Arch./.  Hygiene,  27,  1896. 
