479 
association  with  swampy  ground,  but  until  comparatively  recent  years 
nothing  was  known  as  to  its  causation.  It  has  been  attributed  to 
many  things — to  the  bad  air  or  miasmata  emanating  from  swamps 
(hence  the  name  Mai  Aria),  to  animalculae,  inhaled  from  the  air  of 
swamps,  to  small  vegetable  cells,  and  to  bacilli.  But  the  relationship 
between  these  various  supposed  causes  and  malarial  fevers  was  never 
proved,  and  it  was  not  until  1880  that  the  discovery  of  the  parasite 
of  malarial  fever  was  made.  In  that  year  Dr.  Laveran,  a  young  officer 
of  the  French  army  working  in  Algeria,  discovered  in  human  blood 
a  minute  protoplasmic  body,  which  attacked  the  red  cells,  increased 
in  size,  developed  black  pigment,  and  underwent  certain  changes, 
which  were  found  to  bear  a  definite  relationship  to  the  stages  of  an 
attack  of  malarial  fever. 
Confirmation  of  these  observations  soon  came  from  different  parts 
of  the  world.  In  Italy,  India,  America,  in  fact,  in  every  locality  in 
which  malaria  existed,  observers  recognised  and  identified  similar 
bodies,  and  it  was  quite  clear  that,  at  last,  the  definite  cause  of  malaria 
had  been  determined.  But  though  many  additions  to  the  life  history 
of  the  parasite  in  the  human  body  were  made  from  time  to  time,  and 
it  was  successfully  transmitted  from  one  individual  to  another,  by 
means  of  injections  of  blood,  for  many  years  the  method  of  its 
entrance  into  the  human  body  was  unknown.  It  was  evident  that  it 
was  not  infectious,  that  is  to  say,  it  was  not  communicable  directly 
from  one  individual  to  another  by  contact  or  proximity.  It  was 
thought  that  possibly  the  protozoal  organisms  lived  in  the  water  or 
soil  of  marshes,  that  they  bred  there,  developed  some  form  which  was 
capable  of  aerial  transmission  and  gained  admission  to  the  human 
body  by  inhalation.  Others  thought  that  drinking  water  was  the 
medium  of  infection,  but  no  proof  was  forthcoming  of  these  theories, 
nor  was  it  found  possible  to  isolate  any  similar  organisms  in  the  soil, 
water  or  air  of  marshes. 
In  1895,  however.  Professor  Ronald  Ross,  then  a  medical  officer 
of  the  Indian  Army,  now  of  the  Liverpool  School  of  Tropical 
Medicine,  began  an  experimental  study  of  a  hypothesis  which  had 
been  suggested,  but  which,  up  to  that  time,  had  been  purely  specu¬ 
lative,  namely,  that  the  mosquito  was  possibly  the  agent  by  which 
malaria  was  transmitted  from  individual  to  individual ;  and  by  a  series 
of  painstaking  and  brilliant  researches,  he  succeeded  in  demonstrating 
