﻿388 
  W. 
  B. 
  JOHNSON 
  AND 
  LLEWELLYN 
  LLOYD. 
  

  

  has 
  more 
  significance 
  than 
  the 
  25 
  per 
  cent, 
  and 
  1 
  1 
  per 
  cent, 
  given 
  for 
  palpalis 
  and 
  

   tachinoides 
  respectively, 
  since 
  much 
  of 
  the 
  latter 
  is 
  known 
  to 
  be 
  drawn 
  from 
  cattle 
  

   and 
  goats. 
  Undoubtedly 
  morsitans 
  draws 
  the 
  bulk 
  of 
  its 
  food 
  from 
  antelopes 
  and 
  

   pigs. 
  Non-mammalian 
  blood 
  was 
  found 
  in 
  four 
  cases 
  out 
  of 
  97 
  recognisable 
  bloods, 
  

   as 
  usual, 
  a 
  very 
  small 
  proportion. 
  

  

  VI. 
  — 
  Trypanosome 
  Infections 
  in 
  Tsetse-flies. 
  

  

  This 
  section 
  deals 
  with 
  a 
  part 
  of 
  the 
  investigation 
  which 
  is 
  at 
  the 
  time 
  of 
  writing 
  

   very 
  incomplete, 
  but 
  a 
  brief 
  account 
  of 
  it 
  is 
  essential 
  for 
  the 
  purposes 
  of 
  this 
  report. 
  

   A 
  preliminary 
  examination 
  of 
  the 
  stained 
  slides 
  was 
  made 
  as 
  the 
  material 
  accumulated, 
  

   but 
  a 
  more 
  critical 
  study 
  of 
  these 
  could 
  not 
  be 
  carried 
  out 
  until 
  a 
  large 
  number 
  had 
  

   been 
  collected. 
  This 
  critical 
  examination 
  is 
  now 
  in 
  progress 
  and 
  a 
  fuller 
  account 
  

   will 
  be 
  issued 
  when 
  it 
  is 
  complete. 
  

  

  Flies 
  of 
  the 
  four 
  species 
  met 
  with 
  were 
  dissected. 
  The 
  living 
  fly 
  was 
  held 
  between 
  

   the 
  finger 
  and 
  thumb, 
  and 
  gentle 
  pressure 
  was 
  applied 
  from 
  behind 
  forwards 
  until 
  

   the 
  proboscis 
  was 
  depressed 
  as 
  in 
  the 
  act 
  of 
  feeding. 
  A 
  needle 
  was 
  then 
  placed 
  on 
  

   the 
  front 
  of 
  the 
  head 
  and 
  in 
  most 
  cases 
  a 
  small 
  drop 
  of 
  salivary 
  fluid 
  appeared 
  at 
  the 
  

   tip 
  of 
  the 
  proboscis. 
  This 
  exudate, 
  called 
  the 
  " 
  salivary 
  drop," 
  was 
  received 
  on 
  a 
  

   slide 
  with 
  a 
  smearing 
  motion. 
  The 
  fly 
  was 
  then 
  dissected, 
  the 
  salivary 
  glands, 
  

   proventriculus, 
  gut 
  and 
  proboscis 
  (with 
  a 
  note 
  about 
  the 
  hypopharynx) 
  were 
  mounted 
  

   and 
  examined 
  separately. 
  Any 
  organs 
  containing 
  flagellates 
  were 
  transferred 
  to 
  

   a 
  small 
  drop 
  of 
  saline 
  on 
  a 
  clean 
  slide, 
  teased 
  up, 
  dried 
  rapidly, 
  fixed 
  with 
  absolute 
  

   alcohol, 
  and 
  stained 
  with 
  Giemsa's 
  stain, 
  12-18 
  hours 
  in 
  a 
  2-3 
  per 
  cent, 
  solution. 
  

   Thanks 
  mainly 
  to 
  the 
  work 
  of 
  the 
  Royal 
  Society's 
  Sleeping 
  Sickness 
  Commissions, 
  

   especially 
  the 
  one 
  in 
  Nyasaland 
  under 
  Sir 
  David 
  Bruce 
  (4), 
  it 
  is 
  possible 
  to 
  refer 
  the 
  

   tsetse-borne 
  pathogenic 
  trypanosomes 
  to 
  the 
  three 
  main 
  groups 
  when 
  the 
  infection 
  

   in 
  the 
  fly 
  is 
  mature. 
  This 
  is 
  done 
  partly 
  by 
  their 
  position 
  in 
  the 
  fly 
  and 
  partly 
  by 
  

   the 
  morphology 
  of 
  the 
  infective 
  forms, 
  which 
  resemble 
  blood 
  forms 
  and 
  are 
  group- 
  

   specifically 
  distinct. 
  Briefly, 
  the 
  brucei-gambiense 
  group 
  develop 
  in 
  the 
  gut, 
  pass 
  

   forward 
  to 
  the 
  proventriculus 
  and 
  so 
  to 
  the 
  salivary 
  glands, 
  where 
  the 
  infective 
  

   forms 
  are 
  found 
  ; 
  the 
  proboscis 
  plays 
  no 
  part 
  in 
  their 
  development. 
  The 
  pecorum 
  

   group 
  also 
  develop 
  in 
  the 
  gut 
  and 
  pass 
  forward 
  to 
  the 
  proventriculus 
  and 
  proboscis, 
  

   the 
  infective 
  forms 
  being 
  found 
  in 
  the 
  hypopharynx, 
  and 
  the 
  salivary 
  glands 
  being 
  

   not 
  involved. 
  The 
  vivax 
  group 
  is 
  confined 
  in 
  its 
  development 
  to 
  the 
  proboscis, 
  

   the 
  infective 
  forms 
  being 
  found 
  in 
  the 
  hypopharynx. 
  There 
  is 
  also 
  the 
  possibility 
  

   that 
  non-pathogenic 
  forms, 
  such 
  as 
  T. 
  grayi 
  found 
  in 
  the 
  gut 
  of 
  palpalis, 
  may 
  be 
  

   encountered, 
  while 
  an 
  infection 
  of 
  gut 
  and 
  proboscis 
  in 
  a 
  wild 
  fly, 
  if 
  judged 
  only 
  by 
  

   position, 
  might 
  be 
  due 
  to 
  a 
  double 
  infection 
  with 
  the 
  vivax 
  group 
  and 
  one 
  of 
  the 
  gut 
  

   developing 
  forms, 
  or 
  it 
  might 
  be 
  a 
  pure 
  pecorum 
  group 
  infection. 
  These 
  facts 
  detract 
  

   from 
  the 
  value 
  of 
  the 
  almost 
  entirely 
  statistical 
  data 
  which 
  we 
  are 
  at 
  present 
  able 
  

   to 
  give. 
  

  

  The 
  results 
  obtained 
  by 
  means 
  of 
  the 
  salivary 
  drop 
  were 
  disappointing. 
  It 
  was 
  

   hoped 
  that 
  it 
  would 
  be 
  a 
  simple 
  and 
  rapid 
  method 
  of 
  finding 
  infective 
  flies, 
  but 
  this 
  

   proved 
  not 
  to 
  be 
  the 
  case. 
  The 
  amount 
  of 
  material 
  exuded 
  was 
  uneven, 
  and 
  when 
  

   a 
  large 
  smear 
  was 
  obtained 
  it 
  was 
  impervious 
  to 
  stain, 
  the 
  trypanosomes 
  appearing 
  

   like 
  ghosts 
  in 
  a 
  dark 
  matrix, 
  with 
  nuclei, 
  undulating 
  membrane 
  and 
  flagellum 
  

   faintly 
  indicated. 
  This 
  difficulty 
  may 
  be 
  overcome 
  by 
  receiving 
  the 
  salivary 
  drop 
  

   in 
  a 
  small 
  drop 
  of 
  serum, 
  when 
  very 
  good 
  fixation 
  and 
  staining 
  is 
  obtained. 
  More- 
  

   over, 
  many 
  infective 
  flies 
  were 
  found 
  by 
  dissection, 
  as 
  indicated 
  by 
  the 
  presence 
  

   of 
  the 
  infective 
  forms 
  of 
  trypanosomes, 
  in 
  which 
  none 
  were 
  extruded 
  on 
  the 
  slide. 
  

   Nevertheless 
  many 
  infective 
  forms 
  belonging 
  to 
  the 
  pecorum 
  and 
  vivax 
  groups 
  were 
  

   thus 
  obtained, 
  and 
  the 
  method 
  of 
  examination, 
  similar 
  to 
  one 
  employed 
  by 
  Bruce, 
  

   is 
  not 
  without 
  its 
  value, 
  though 
  of 
  no 
  use 
  for 
  statistical 
  purposes. 
  

  

  