And  these,  as  I  have  already  shown,  will  depend  upon  two 
factors 
(a)  the  infected  mosquito,  and 
(b)  the  infected  individual. 
(a)  Mosquito  reduction:  It  is  evident  that  in  a  well  watered 
island  like  Jamaica,  with  large  areas  under  cultivation,  it  is  out  of 
the  question  to  hope  for  the  complete  extermination  of  the  mosquito. 
But  this  is  not  necessary :  a  reduction  in  the  number  of  mosquitoes  is 
sufficient,  and  this  can  be  effected  with  little  difficulty. 
I  do  not  propose  here  to  enter  into  a  discussion  of  the  factors 
which  govern  the  numbers  and  diffusion  of  Anophelines  in  any  given 
locality,  but  would  refer  those  who  wish  to  study  this  part  of  the 
subject  more  minutely  to  other  scientific  papers,  and  especially  to 
Professor  Ross’s  Report  on  Malaria  in  Mauritius.  But  it  is  self- 
evident  that  the  further  off  a  breeding  place  is  from  an  inhabited 
locality,  the  fewer  mosquitoes  will  reach  the  inhabitants  of  that  spot. 
If  we  have  two  pools  in  the  neighbourhood  of  a  town,  A  at  50  yards 
breeding,  say,  100  Anophelines,  and  B  at  100  yards  breeding  the  same 
number,  if  we  can  so  treat  breeding  pool  A  that  the  Anophelines  do 
not  breed  there,  we  have  diminished  very  largely  the  probabilities  of 
Anophelines  reaching  the  inhabitants  from  the  distant  breeding  pool 
B.  So  that  the  problem  does  not  involve  the  destruction  of 
mosquitoes  over  large  areas,  but  resolves  itself  into  their  extermina¬ 
tion  or  reduction  in  the  immediate  vicinity  of  inhabited  places  ;  and 
it  has  been  shown  by  practical  experience  elsewhere  (see  note  on 
Federated  Malay  States)  that  mere  reduction  is  sufficient  to  cause  a 
large  diminution  in  the  amount  of  malaria.  And  if  to  these  we  add  a 
reduction  in  the  number  of  infected  individuals  by  various  means,  we 
get  a  still  further  proportionate  diminution  in  the  amount  of  malaria. 
(i)  Rivers  and  .  Swamps,  The  first  step,  and  the  most 
important  as  affording  eventually  a  permanent  solution  of  the 
problem,  is  of  course  the  drainage  and  filling  in  of  swamps  in  the 
immediate  vicinity  of  towns.  Most  of  the  principal  towns  are 
situated  at  the  mouth  of  rivers,  and  consequently  are  surrounded  by 
swamps.  But  I  recognise  that  this  is  a  very  large  engineering  question, 
and  if  an  attempt  were  made  to  overtake  it  at  once,  would  involve  an 
expenditure  of  public  money  which  is  out  of  the  question.  So  that 
