3i6 
Disinfection. 
Am.  Jour  Pharni. 
July,  1915. 
far-reaching  than  his,  since  he  shares  with  Pasteur  the  honor  of  dem- 
onstrating the  connection  between  microorganisms  and  processes  of 
infection.  Lister  found  carbolic  acid  to  be  exceedingly  efficient,  and 
recommended  it  highly  because  of  its  ready  adaptability  to  the  proc- 
esses of  aseptic  surgery.  While  it  is  fatal  in  three  to  five  per  cent, 
solution  to  the  vegetative  forms  of  microbial  life,  it  is  not  always 
effective  against  spores  in  any  dilution  or  even  in  pure  form  except  at 
high  temperatures.  However,  because  of  retaining  its  effectiveness 
in  the  presence  of  salts,  acids,  alkalies,  and  even  protein,  it  ranks  above 
mercuric  chloride  for  some  purposes,  although  under  ideal  conditions 
the  latter  is  many  times  as  efficient. 
That  portion  of  coal-tar  oil  which  remains  after  phenol  is  removed 
was  first  recognized  as  having  antiseptic  value  when  it  was  used  for 
pickling  timber,  a  process  patented  in  1836  in  England.  It  is  still  an 
open  question  what  constituent  of  the  heavy  coal-tar  oils  is  most  valu- 
able as  a  preservative,  but  its  use  for  this  purpose  served  to  direct 
attention  to  the  strongly  germicidal  character  of  certain  of  its  con^ 
stituents.  A  part  of  the  oil,  later  known  as  creosote  oil  because  of 
its  similarity  to  wood  creosote,  was  prepared  as  a  disinfectant  as 
early  as  1874.  The  first  preparation  of  importance  was  that  known  as 
creolin,  prepared  in  1887.  It  was  analyzed,  and  its  composition  made 
known  to  the  scientific  world  in  1889.  Since  that  time  the  number  of 
such  preparations  has  increased  enormously,  and  at  the  present  time 
there  are  hundreds  of  the  coal-tar  disinfectants  composed  of  creosote 
oil  and  soap  and  containing  various  proportions  of  phenols.  The 
germicidal  values  of  these  range  from  that  with  a  coefficient  of  1,  or 
about  equal  to  pure  phenol,  to  those  of  exceptional  value  with  coeffi- 
cients of  10  or  more,  depending  on  the  amount  and  character  of  the 
phenols  present. 
The  phenol  coefficient  is  a  term  used  to  designate  the  value  of  a 
germicide.  Since  carbolic  acid  or  phenol  is  well  known  as  an  efficient 
disinfectant,  its  value  is  taken  as  unity,  and  the  value  of  any  other 
substance  similarly  used  can  be  expressed  by  a  number  called  its  co- 
efficient, which  indicates  how  many  times  more,  or  in  some  cases  less, 
the  disinfectant  can  be  diluted  than  phenol  and  retain  an  equal  germi- 
cidal value.  Because  of  the  infinite  variety  of  combinations  in  coal 
tar,  a  chemical  assay  will  not  give  a  very  accurate  indication  of  the 
efficiency  of  an  oil.  Its  real  value  can  be  ascertained  only  by  actual 
comparison  with  phenol,  using  B.  typhosus  as  the  test  organism,  and 
