352 
The  blepharoplast  is  not  quite  terminal  (o'5  to  ro  fi  from  the 
end) ;  the  nucleus  is  oval  or  compressed,  and  is  placed  rather 
towards  the  posterior  extremity.  The  undulating  membrane  is  rudi¬ 
mentary,  and  there  is  no  appreciable  free  flagellum.  The  posterior 
extremity  is  rounded  or  bluntly  conical.  The  cytoplasm  is  commonly 
homogeneous,  but  in  some  slides  a  considerable  proportion  show  a 
clear  area  (?  vacuole)  near  the  blepharoplast,  whilst  many  exhibit 
a  few  fine  chromatic  granules  between  the  blepharoplast  and  the 
nucleus.  The  greatest  width  is  posterior  to  the  nucleus. 
Diagnosis 
From  its  morphology  it  is  quite  evident  that  this  trypanosome  is 
not  related  to  the  evansi  group  ;  and  by  its  pathogenicity  to  small 
animals  it  is  separable  from  the  vivax  group,  and  consequently  from 
T.  nannm,  though  on  morphological  grounds  alone  it  would  be 
impossible  to  distinguish  it  from  the  tadpole  forms  of  this  latter. 
According  to  our  rough  grouping* * * §  it  would  fall  under  the  head  of 
dimorfhon,  here  containing  the  three  named  forms  T.  dimorphon, 
T.  congolense,  and  T.  pecaiidi.  Owing  to  the  entire  absence  of  long 
free-flagellated  forms,  and  the  accompanying  broad  individuals  with 
well-developed  undulating  membrane,  the  last  named  may  be 
excluded.  We  have  then  to  discuss  the  properties  of  T.  dimorphon 
and  T.  congolense,  the  only  remaining  named  species,  and  to  ascertain 
to  which  the  organism  from  Balungu  most  closely  approximates.  It 
is  to  be  noted  that  the  ‘  animal  reactions  ’  in  all  these  are  closely 
similar. 
According  to  the  original  descriptions  of  Dutton  and  Todd,t 
T.  dimorphon  occurs  in  at  least  two  forms  : — (i)  a  tadpole  similar  to 
that  which  we  have  just  described,  and  (2)  a  long  form  carrying  a  free 
flagellum.  Intermediate  forms,  termed  stumpy,  may  also  be  found. 
This  parasite  was  found  in  the  Gambia,  where  ten  horses  were 
detected  as  suffering  from  trypanosomiasis.  Of  these,  four  were  used 
for  experimental  observation — Cases  i,  5,  6  and  9.  Case  6  was 
brought  to  England  and  served  for  the  experimental  work  carried  out 
by  Thomas  and  Breinlf  and  by  Laveran  and  Mesnil.§  Practically  all 
*  Montgomery  R.  E.  and  Kinghorn,  A.  Ann.  Trof.  Med.  Parasitol .,  1909,  If 
5.  PP-  333-344-  ^  ^  .  ,7  1  V 
t  Dutton  and  Todd.  Thomfson  Yates  and  Johnston  Lab.  Reforts,  1903,  Vol.  v. 
-^TUnmne  anH  Rre.inE  Thomi)son  Yates  and  Johnston  Lab.  Re-ports,  loo?,  Vol. 
\T,  II. 
§  Laveran  and  Mesnil.  Trypanosomes  et  Trypanosomiases. 
