HEALTH  PRECAUTIONS  369
they  reach  reservoirs,  are  used  for  washing
clothes  or  bathing  and  become  infected  in  this
manner.  It  is  obviously  out  of  the  question  to
boil  all  water  prior  to  drinking  and  if  you  are
obliged  to  take  many  trips  to  the  interior  or  off
the  beaten  paths  of  travel,  bottled  mineral
waters  are  not  always  obtainable.  Therefore
it  is  wise  for  the  purposes  of  such  excursions  to
carry  any  of  the  well-known  makes  of  pocket
filter,  which  come  especially  made  for  such
purposes.  Let  me  take  advantage  of  this  opportunity ­
  to  correct  the  erroneous  idea  entertained ­
  by  so  many  of  the  laity  that  locally  made
aerated  mineral  waters  are  free  from  bacteria.
They  should  be  shunned  as  much  as  the  local
unboiled  water.  The  best  thing  to  do  if  you
are  going  to  these  countries,  is  to  have  your
system  rendered  immune  to  the  typhoid
bacillus,  by  having  your  family  physician  give
you  the  anti-typhoid  vaccination,  such  as  is
used  in  the  American  army  and  navy.  There
is  but  little  inconvenience  attending  its  administration ­
  and  you  can  rest  assured  that  after
taking  the  treatment  you  will  not  contract