were  possible  to  ensure  that  all  matter  likely  to  be  a  source  of  con-
tagion were  liberally  supplied  with  the  oxygen  of  the  air.  The
oxidation  of  the  products  of  those  niicro-organisms  which  are  poisonous
to  man,  such  as  the  "  ptomaines  "  and  "  toxines,"  which  Selmi  was  the
first  to  investigate,  is  no  easy  task.  The  bacteria  which  produce  these
toxic  compounds  have  a  higher  vitality  than  man,  and  most  strong
chemical  agents  which  can  kill  bacteria  have  also  a  toxic  effect  upon
more  complex  organisms.  No  man  can  endure  an  atmosphere  that
will  kill  these  bacteria.  Only  the  halogens,  chlorine,  bromine,  and
iodine  can  penetrate  their  envelopes,  and  these  cannot  be  given  in
sufficient  quantity  when  man  is  present.  It  is,  therefore,  absolutely
iiecessary  to  remove  patients  and  seal  rooms  in  order  that  disinfection
may  be  successfully  accomplished.
The  importance  of  the  distinction  between  an  antiseptic,  which
simply  stupefies  the  germs  of  disease  for  a  time,  and  a  disinfectant,
-which  kills  them  and  leaves  the  room  sterile,  cannot  be  too  strongly
insisted  upon.  The  use  of  antiseptics  merely  puts  off  the  era  of  putre-
faction, and  while  arresting  temporarily  the  evil,  does  not  eradicate  it.
The  "  molecular"  or  ordinary  oxygen  of  the  air  acts  slowly.  When
liberated  from  various  chemical  compounds  like  permanganate  and
peroxide  of  hydrogen  it  is  said  to  be  in  a  "  nascent '"'  or  atomic  con-
<iition,  and  is  then  far  more  active.
