Disease  Reservoirs.  —  Although  offensive  warfare
against  the  germs  of  disease  finds  its  most  important
method  of  attack  in  the  means  by  which  germs  are  kept


GERM   FIGHTING:   OFFENSIVE   METHODS        365

from  passing  from  one  person  to  another,  complete  success
in  disease  prevention  cannot  be  attained  through  this
method  alone.  Ultimate  victory  depends  upon  our  finding
out  and  doing  away  with  the  harboring  places  of  germs
during  the  periods  when  there  are  no  outbreaks  of  disease.
Though  lacking  in  our  knowledge  of  such  harboring  places,
or  reservoirs,  it  is  known  that  some  such  place  or  condition
exists  for  the  germs  of  each  of  the  infectious  diseases.  We
already  have  a  clue  to  possible  typhoid  reservoirs  in  the
typhoid  carriers  (page  354),  to  malarial  reservoirs  in  the
continued  existence  of  germs  in  the  blood  of  convalescent
malarial  patients,  to  tuberculosis  reservoirs  in  the  preva-
lence of  this  disease  among  cattle,  and  to  plague  reser-
voirs in  the  prevalence  of  plague  among  rats.  Germs  are
also  known  to  exist  in  an  inactive  state  in  clothing,  in  the
furniture,  fixtures,  and  walls  of  rooms,  and  in  soils,  and  to
remain  so  for  rather  long  periods  of  time.  As  our  knowl-
edge in  this  field  increases  we  may  hope  to  destroy  the
more  important  of  the  germ  species  causing  disease.
