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XXV.  The  Origin  of  Malaria.     By  Daniel  Vaughan*. 
To  the  Editors  of  the  Philosophical  Magazine  and  Journal, 
Gentlemen,  Cincinnati,  December  30,  18/1. 
I  SHOULD  like  to  submit  to  scientific  men  a  brief  exposition 
of  my  researches  on  Malaria,  as  I  think  they  will  be  re- 
ceived with  some  degree  of  interest.  The  present  communica- 
tion contains  the  chief  points  given  in  two  papers  at  the  Academy 
of  Medicine  of  this  city ;  but  it  is  prepared  with  more  care  and 
better  adapted  to  the  character  of  the  Philosophical  Magazine. 
Hoping  that  you  will  give  it  publication  at  your  earliest  conve- 
nience, 
I  remain, 
Yours  very  truly, 
Daniel  Vaughan. 
"While  excessively  moist  lands  in  warm  climates  are  known  to 
be  very  unfavourable  to  health,  no  adequate  cause  for  the  evils 
is  to  be  found  in  the  local  variation  in  the  gaseous  constituents 
of  the  air,  or  in  any  direct  influence  of  the  aqueous  vapour 
which  it  contains.  To  remove  the  mysteries  connected  with  the 
insalubrity  of  such  localities,  the  course  of  experimental  inquiry 
has  recently  been  directed  to  a  search  for  the  organic  matter  in 
air  and  in  water ;  but  an  examination  of  the  sources  from  which 
this  matter  is  derived  may  contribute  much  to  reveal  its  pecu- 
liar characters  and  its  effects  on  the  human  frame.  For  the 
greater  portion  of  the  carbonaceous  matter  which  it  contains 
the  atmosphere  is  indebted  to  the  vegetable  kingdom ;  and  to 
this  great  repository  of  carbon  we  may  first  look  for  the  source 
of  marsh-poison,  which  is  generally  regarded  as  having  a  vegetable 
origin. 
Though  serious  evils  may  be  justly  imputed  to  the  dust 
which  occasionally  floats  around  us,  they  must  be  excluded  from 
consideration  in  inquiries  respecting  the  insalubrity  of  marshes. 
In  these  permanent  abodes  of  moisture  dust  cannot  be  ex- 
pected to  rise  from  the  ground  ;  and  its  solid  particles  would 
be  only  removed  from  the  air  by  those  rains  which  observation 
proves  to  be  instrumental  in  developing  the  activity  of  malaria. 
Alkaloids,  vegetable  acids,  and  the  salts  which  they  form  might 
mingle  with  the  fresh  waters  of  our  lands ;  yet  they  cannot 
be  expected  to  pass  into  the  air  in  a  quantity  sufficient  to  affect 
in  a  serious  degree  the  economy  of  animal  life.  But  the  vola- 
tile oils  emitted  by  living  and  decaying  plants  have  the  greatest 
tendency  to  charge  the  air  with  their  vapours;  and  as  the 
extent  of  this  impregnation  depends  chiefly  on  heat,  they  appear 
*  Communicated  by  tbe  Author. 
Phil  Mag,  S.  4.  Vol.  43.  No.  285.  March  1872.  P 
