^o^ms?**}     Mm  Action  etc.  of  Disinfectants.  505* 
ing  the  air.  It  is  therefore  useless  to  try  to  disinfect  the  air.  This 
is  strikingly  illustrated  in  reference  to  printed  directions  relative  to* 
the  practice  of  disinfection.  See,  for  instance,  Dr.  Wilson's  little- 
card,  "  Disinfectants  and  how  to  use  them." 
"  Chlorine  gas,  poisonous  and  irritating  to  the  lungs  when  in  ex- 
cess. For  an  occupied  room,  close  fire-place,  windows,  etc.,  as  di- 
rected under  F.  Pour  over  a  quarter  of  a  pound  of  black  oxide  of" 
manganese  in  a  dish  placed  high  half  a  pint  of  muriatic  acid  (spirit  of 
salt),  and  leave  for  six  hours.  It  bleaches,  and  is  apt  to  make  white- 
limed  walls  sweat — useful  for  cabs." 
Now  if  we  take  a  room,  say  13  feet  by  13  feet  and  13  feet  high,, 
or  of  a  capacity  of  about  39  cubic  metres  (and  that  is  not  a  very 
large  room),  and  if  we  calculate  what  proportion  by  weight  the  chlo- 
rine liberated  by  the  quarter  of  a  pound  of  oxide  of  manganese  will 
amount  to,  we  get  about  3  parts  of  chlorine  in  1000  parts  of  air.  In 
point  of  fact,  however,  the  proportion  of  chlorine  in  the  atmosphere 
of  such  a  room  would  never  reach  anything  like  3>  per  1000,  inasmuch 
as  walls  are  not  impervious,  and  during  the  six  hours  the  air  would 
have  changed,  and  3  parts  per  10,000  would  probably  be  nearer  the 
true  proportion.  But  this  is  the  room  not  fit  to  inhabit  by  reason  of 
the  presence  of  chlorine.  The  minuteness  of  the  dose  of  chlorine 
which  the  inhabited  room  receives  may  be  left  to  your  imaginations. 
To  me  it  seems  that  the  wisdom  of  the  physician  who  places  his  little 
saucer  with  bleaching  powder  and  muriatic  acid  in  the  chamber  of  his 
patient,  is  comparable  with  that  of  the  cattle-plague  commissioners 
who  tied  the  carbolized  cloths  to  the  horns  of  the  cattle. 
Experience  confirms  that  which  an  appeal  to  first  principles  sug- 
gests ;  and  we  are  informed  that,  during  the  Franco-German  war,, 
although  the  hospitals  stank  of  carbolic  acid,  yet  wounds  were  not 
healthy.  Although  I  believe  that  the  purification  of  air  which  has- 
once  been  defiled  is  a  hopeless  task,  yet  it  by  no  means  follows  that 
disinfectants  have  nothing  to  do  with  purity  of  atmosphere.  It  is 
open  to  us  to  abstain,  in  a  very  large  degree,  from  rendering  the  air 
impure. 
By  the  efficient  application  of  disinfectants  to  foul  surfaces,  we 
may  hinder  defilement  of  the  atmosphere  of  oar  dwellings.  One  of 
the  main  functions  of  a  serviceable  disinfectant  is  that  it  shall  be  an- 
tiseptic ;  that  it  shall  postpone  decomposition  and  putrefaction  until 
a  convenient  season.   A  good  disinfectant  should  not  itself  defile  air„ 
