These  cases  can  only  be  found  by  a  systematic  search  by  properly 
qualified  medical  men. 
At  the  same  time,  medical  men  can  do  other  most  useful  work  in 
maiDpmg  out  the  distribution  of  vairious  biting  insects,  and  conducting 
preliminary  enquiries  into  the  incidence  of  cattle  and  other  diseases. 
However,  it  should  be  distinctly  understood  that  the  work  in 
connection  with  Sleeping  Sickness  is  sufficiently  arduous  to  require 
undivided  attention,  and  the  tendency  which  occasionally  is  seen  to 
add  this  work  to  the  duties  of  the  ordinary  district  medical  officers 
can  only  result  in  the  work  being  indifferently  executed. 
This  also  applies  to  the  clean  areas  of  N.E.  Rhodesia,  for  it  must 
not  be  forgotten  that  the  first  case  of  human  trypanosomiasis 
diagnosed  there  was  at  Chinsali,  on  the  Tanganyika-Nyasa  plateau, 
where  no  Gl.  fal falls  exist. 
The  natives  should  be  encouraged  to  apply  for  passes  when  they 
are  about  to  travel.  Provided  no  unnecessary  difficulties  are  placed 
in  the  way  of  these  being  obtained,  the  natives  will,  in  time,  apply 
for  them  as  a  matter  of  course.  We  found  that  whenever  we  had 
occasion  to  send  a  messenger,  he  would  always  come  up  and  ask  for 
a  note  before  leaving. 
The  eventual  fate  of  both  Rhodesia  and  Nyasaland,  to  say  nothing 
of  other  territories  which  bound  them,  depends  on  what  species  of 
tsetse  flies  can  convey  the  disease  in  nature.  Gl.  falfalis  has 
only  a  comparatively  small  distribution,  so  far  as  we  know,  but  that  of 
Gl.  morsitans  is  extremely  wide,  so  that  if  this  species  can 
transmit  T.  gambiense  the  greatest  danger  exists. 
It  IS  admitted  that  mechanical  transmission  is  possible,  but 
whether  it  plays  a  very  extensive  role  in  nature,  in  determmmg 
the  spread  of  the  disease,  is  questioned.  In  any  case,  the  odds 
against  it  occurring  are  enormous,  for  even  in  laboratory  experiments 
with  Gl.  falfalis,  the  number  of  flies  which  has  been  required  for  a 
successful  result  is  extremely  large,  and  the  conditions  under  which 
these  experiments  have  been  carried  out  in  the  laboratory  would  occur 
but  very  seldom  m  nature.  Whether,  however,  the  position  that  the 
possibility  of  it  happening  in  nature  can  be  ignored,  is  rather  question¬ 
able.  We  believe  that  mechanical  transmission  is  responsible  for  the 
spread  of  certain  cattle  trypanosomes,  and  some  support  for  the 
supposition  that  it  may  take  place  in  the  human  disease  is  afforded 
