^selrimT'}  Theory  of  Disinfectants.  415 
oring  to  supply  a  more  probable  theory,  it  may  be  well  to  remind 
you  that  the  researches  already  mentioned  have  established  the  fact 
that  contagion  and  putrefaction,  if  not  actually  identical,  are  processes 
so  closely  allied  that  they  require  exactly  similar  conditions ;  the 
latter  appearing  to  consist  of  a  kind  of  disease  propagated  from  par- 
ticle to  particle  of  a  decomposing  substance,  and  ending  in  its  entire 
destruction.  Hence  it  may  be  inferred  with  perfect  safety,  that  any 
agent  which  arrests  putrefaction  is  capable  also  of  abolishing  the 
properties  of  contagion  and  infection. 
This  conclusion  at  once  puts  into  our  hands  a  valuable  instrument 
of  research ;  for  while  it  is  difficult,  and  often  impossible,  to  investi- 
gate directly  the  disinfectant  action  of  a  substance,  the  inquiry  being 
surrounded  by  innumerable  sources  of  error,  the  properties  of  an 
antiseptic  are  perfectly  well  defined  and  open  to  the  clearest  demon- 
stration. Thus,  in  the  case  of  the  two  bodies  mentioned  above,  car- 
bolic acid  and  chloride  of  aluminium,  the  antiseptic  action  of  the  first 
is  well  known,  and  has  long  been  usefully  applied  ;  while  that  of  the 
latter  is  maintained  in  the  most  positive  manner  by  its  introducer, 
Mr.  John  Gamgee,  who  certainly  brings  forward  overwhelming  proof 
of  it  in  his  recorded  experiments  upon  meat  and  fish  ;  and  hence,  on 
the  ground  given,  we  are  justified  in  regarding  these  substances  as 
good  and  useful  disinfectants.  It  may  be  stated,  in  passing,  that  the 
deodorizing  power  which  these  and  other  similar  bodies  possess  is 
probably  due  to  their  antiseptic  action;  the  ofi'ensive  gases  of  decom- 
position being  sooner  lost  by  diffusion,  and  their  fresh  production 
being  entirely  suspended. 
Let  us  now  proceed  to  a  consideration  of  the  origin  of  the  remark- 
able properties  which  we  have  described.  This  appears  to  have  been 
traced  with  some  degree  of  probability,  in  the  case  of  carbolic  acid, 
by  Dr.  Joseph  Hirsch,  the  writer  of  an  article  which  appeared  in  the 
Chemical  News  about  the  end  of  February,  1869.  He  advances  the 
bold  and  ingenious  speculation,  that  the  disinfectant  action  of  that 
substance  depends  upon  its  power  of  coagulating  albumen.  He  sup- 
poses that  the  acid  finds  its  way  into  the  minute  organisms,  which 
propagate  disease  by  diffusion  through  their  investing  membrane ; 
that  it  coagulates  the  albumen  which  they,  in  common  with  all  ger- 
minal matter,  contain  as  a  necessary  constituent ;  and  thus  practically 
destroys  their  vitality  as  perfectly  as  immersion  in  boiling  water  ter- 
minates that  of  an  egg. 
