﻿224 
  PEOCEEDINGS 
  OF 
  THE 
  FOURTH 
  ENTOMOLOGICAL 
  MEETING 
  

  

  realize 
  that 
  the 
  production 
  of 
  disease 
  is 
  a 
  mere 
  accident 
  from 
  the 
  point 
  

   of 
  view 
  of 
  the 
  Trypanosome, 
  an 
  occurrence 
  which 
  is 
  fatal 
  to 
  itself 
  as 
  

   well 
  as 
  to 
  its 
  involuntary 
  host, 
  should 
  the 
  latter 
  die. 
  In 
  the 
  case 
  of 
  

   wild 
  animals 
  which 
  carry 
  the 
  Trypanosomes 
  producing 
  Sleeping 
  Sickness 
  

   and 
  Nagana 
  in 
  Africa, 
  these 
  parasites 
  live 
  without 
  doing 
  harm 
  to 
  their 
  

   hosts 
  although 
  they 
  produce 
  fatal 
  diseases 
  when 
  introduced 
  into 
  hosts 
  

   which 
  are 
  not 
  used 
  to 
  them 
  and 
  which 
  cannot 
  tolerate 
  them 
  and 
  hence 
  

   become 
  diseased. 
  It 
  has 
  been 
  found 
  by 
  cultural 
  methods 
  that 
  normal 
  

   English 
  cattle 
  have 
  Trypanosomes 
  in 
  their 
  blood 
  and 
  it 
  seems 
  certain 
  

   that 
  in 
  India 
  cattle 
  and 
  buffaloes 
  form 
  a 
  normal 
  reservoir 
  for 
  Trypano- 
  

   soma 
  evansi, 
  without 
  its 
  causing 
  them 
  any 
  particular 
  harm. 
  There 
  

   seems 
  to 
  be 
  little 
  exact 
  particular 
  information 
  regarding 
  the 
  degree 
  

   or 
  distribution 
  of 
  such 
  tolerant 
  infestation 
  in 
  either 
  domesticated 
  or 
  

   wild 
  animals 
  in 
  India, 
  but 
  it 
  is 
  as 
  well 
  to 
  realize 
  at 
  the 
  outset 
  that 
  

   infection 
  in 
  the 
  case 
  of 
  hitherto 
  healthy 
  animals 
  may 
  be 
  derived, 
  not 
  

   only 
  from 
  other 
  similar 
  animals 
  which 
  are 
  actively 
  showing 
  the 
  disease, 
  

   but 
  from 
  other 
  animals 
  which 
  may 
  appear 
  quite 
  healthy. 
  To 
  detect 
  

   the 
  presence 
  of 
  the 
  parasite 
  in 
  such 
  apparently 
  healthy 
  animals 
  is 
  not 
  

   always 
  easy, 
  as 
  it 
  may 
  only 
  appear 
  occasionally 
  in 
  the 
  peripheral 
  circu- 
  

   lation 
  ; 
  the 
  Twentyfourth 
  Annual 
  Keport 
  of 
  the 
  Bureau 
  of 
  Animal 
  

   Industry, 
  United 
  States 
  of 
  America 
  (1907), 
  for 
  example, 
  reports 
  a 
  case 
  

   in 
  which 
  Indian 
  cattle 
  were 
  imported 
  into 
  America 
  and 
  examined 
  daily, 
  

   when 
  it 
  was 
  found 
  that 
  the 
  Surra 
  organisms 
  only 
  appeared 
  periodically 
  

   and 
  could 
  be 
  found 
  during 
  a 
  period 
  of 
  2 
  to 
  4 
  days 
  and 
  then 
  remained 
  

   absent 
  for 
  another 
  period 
  of 
  5 
  to 
  6 
  days, 
  after 
  which 
  they 
  reappeared. 
  

   In 
  the 
  case 
  of 
  the 
  camel, 
  Cross 
  (1907) 
  distinguishes 
  an 
  acute 
  form 
  of 
  

   Surra, 
  in 
  which 
  the 
  disease 
  runs 
  a 
  rapid 
  course, 
  the 
  animal 
  dying 
  in 
  a 
  

   few 
  months, 
  and 
  a 
  chronic 
  form, 
  in 
  which 
  the 
  disease 
  is 
  of 
  long 
  duration, 
  

   the 
  animal 
  lingering 
  on 
  from 
  one 
  to 
  three 
  years, 
  becoming 
  gradually 
  

   more 
  and 
  more 
  emaciated 
  and 
  debilitated 
  until 
  death 
  supervenes. 
  So 
  

   that 
  we 
  get 
  cases 
  (1) 
  in 
  which 
  the 
  health 
  of 
  the 
  host 
  is 
  apparently 
  quite 
  

   unaffected, 
  (2) 
  in 
  which 
  the 
  host 
  dies 
  rapidly 
  as 
  the 
  result 
  of 
  infection, 
  

   or 
  (3) 
  cases 
  intermediate 
  between 
  (1) 
  and 
  (2). 
  Pease 
  (1906) 
  states 
  that 
  

   Camel 
  Surra 
  is 
  an 
  attenuated 
  form 
  of 
  horse 
  Surra, 
  and 
  there 
  may 
  be 
  

   differences 
  in 
  strains 
  of 
  the 
  Trypanosome 
  or 
  in 
  individual 
  susceptibility 
  

   of 
  the 
  host 
  ; 
  but 
  these 
  are 
  questions 
  beyond 
  the 
  scope 
  of 
  Entomology 
  

   and 
  which 
  we 
  do 
  not 
  intend 
  to 
  pursue 
  further. 
  

  

  A 
  large 
  mass 
  of 
  information 
  on 
  Surra, 
  especially 
  in 
  horses, 
  was 
  

   accumulated 
  over 
  twenty 
  years 
  ago 
  by 
  Lingard, 
  but 
  his 
  results 
  were 
  

   inconclusive 
  and 
  need 
  not 
  be 
  referred 
  to 
  further. 
  Eogers 
  (1901) 
  seems 
  

   to 
  have 
  been 
  amongst 
  the 
  first 
  to 
  carry 
  out 
  experiments 
  on 
  transmission 
  

   by 
  biting 
  flies. 
  The 
  investigation 
  was 
  done 
  at 
  Muktesar 
  [and 
  as 
  he 
  

  

  