that  the  malarial  parasite  in  man  was  taken  up  by  a  special  variety 
of  mosquito  belonging  to  the  sub-family  Anophelinae,  and  that  it 
underwent  a  series  of  definite  developments  in  the  body  of  the 
mosquito,  culminating  in  the  formation  of  small  thread-like  bodies, 
which  collected  in  the  salivary  glands,  and  were  finally  injected  along 
with  the  salivary  juices  into  the  human  host,  there  to  give  rise  to  an 
attack  of  malarial  fever  similar  to  that  in  the  original  human  host, 
and  characterised  by  identical  parasites. 
These  results  were  very  soon  confirmed  by  other  observers  in 
Italy  and  elsewhere,  and  some  striking  experimental  demonstrations 
of  the  truth  of  this  '  theory  ’  were  given.  A  number  of  Anopheline 
mosquitoes  were  fed  on  a  patient  in  Rome  infected  with  a  mild 
variety  of  malarial  fever,  and  were  forwarded  to  London,  where  a 
volunteer,  the  son  of  Sir  P.  Manson,  submitted  himself  to  the  bites 
of  the  infected  mosquitoes,  with  the  result  that,  although  living  in  a 
locality  where  endemic  malaria  is  now  unknown,  and  without  having 
lived  in  any  other  malarious  locality,  he  developed  a  typical  attack  of 
malarial  fever,  and  parasites,  similar  to  those  in  the  original  patient, 
were  identified  in  the  peripheral  blood.  This  experiment  has  been 
repeated  more  than  once  elsewhere. 
Further,  Doctors  Low  and  Sambon,  living  in  a  mosquito-proof 
house,  in  the  Roman  Campagna,  at  the  most  malarious  season  of  the 
year,  remained  free  from  malaria,  while  all  around  malaria  was 
rampant  among  the  natives  ;  and  that,  without  any  other  precaution 
than  that  of  remaining  within  the  mosquito-proof  house  from  sunset 
to  sunrise,  the  hours  during  which  the  Anopheline  mosquito  (whose 
habits  are  mainly  nocturnal)  came  out  in  quest  of  food. 
It  was  evident,  then,  that  an  enormous  step  in  advance  had  been 
made.  It  had  been  found  that  the  principal  (and  up  to  the  present 
the  only)  method  by  which  malaria  is  transmitted  from  individual  to 
individual  is  by  means  of  a  particular  species  of  mosquito  ;  and  the 
means  of  diminishing,  and  in  some  instances  of  actually  eradicating, 
this  terrible  scourge,  which  for  centuries  has  devastated  the  tropical 
parts  of  the  globe  and  has  rendered  so  many  localities  practically 
uninhabitable,  was  plainly  indicated. 
But  the  attention  which  had  been  drawn  to  the  role  played  by 
mosquitoes  in  the  transmission  of  malaria,  had  suggested  the 
possibility  of  other  tropical  diseases  being  carried  in  the  same  way. 
