353 
Dutton’s  and  Todd’s  work  was  conducted  on  Case  i,  the  strain  from 
which  was  not  used  in  Europe,  and  it  is  from  this  animal  that  the 
raicrophotographs  (Plate  IV,  figs.  2  and  3  of  their  Report),  which 
clearly  show  the  ‘  stumpy  ’  and  the  free-flagellated  ‘  long  ’  forms,  were 
made.  We  elsewhere  analyse  the  published  evidence  on  this  question  ; 
here  it  is  sufficient  to  say  that  we  consider  it  highly  probable  that 
Horses  i  and  6  were  infected  with  distinct  trypanosomes,  one  of 
which  (Plorse  i)  was  the  original  host  of  T.  dimorphon.  The  other 
(Horse  6)  is  the  original  host  of  that  parasite,  which  we  have 
designated  T.  confuswn,  which  at  Liverpool  and  Paris  has  been 
accepted  as  T.  dintoT phon  that  had  undergone  a  peculiar  morpho¬ 
logical  transformation.  We  hold  that  we  have  recovered  T. 
dimorphon  at  Broken  Hill,  thereby  reducing  the  strength  of  an 
argument  that  Dutton  and  Todd  were  concerned  with  an  infection 
by  such  a  trypanosome  as  that  now  known  as  T .  pocciud z,  or  were 
misled  by  a  mixed  infection.  We  consider  that  our  work  at  Broken 
Hill  may  be  considered  to  substantiate  the  species  in  conformity  to  the 
original  description. 
For  a  trypanosome  to  be  regarded  as  T.  dimorphon  it  is  necessary 
that  it  be  shown  to  develop  a  free  flagellum.  From  the  observations 
of  Dutton  and  Todd  in  the  Gambia,  and  ourselves  in  Northern 
Rhodesia,  it  would  appear  that  small  experimental  animals  are  best 
suited  for  this  purpose.  ‘Long’  forms  were  produced  in  all  five 
of  our  guinea-pigs,  and  in  three  out  of  five  white  rats  inoculated  with 
this  strain  of  trypanosome  in  its  first,  second  and  third  passages. 
In  one  rat,  three  guinea-pigs  and  two  dogs  infected  by  the 
‘Balungu’  strain,  we  failed  to  notice  the  development  of  a  free 
flagellum,  or  even  the  occurrence  of  forms  corresponding  to  the  ‘  long 
form  ’  of  Laveran  and  Mesnil.  The  longest  specimen  we  measured 
was  1 6' 3  fi.  The  evidence  is  negative,  but  with  such  as  it  is  we 
cannot  identify  this  trypanosome  with  T.  dimorphon.  It  then  falls 
into  the  group  represented  by  T.  confusum  (T.  dimorphon  of  Paris), 
and  T.  co^igolense.  Laveran*  has  drawn  attention  to  the  differences 
between  these  species.  He  writes  '  Au  point  de  vue  morphologique, 
'Tr.  congolense  differe  de  Tr.  dimorphon.  Le  premier  de  ces 
‘trypanosomes  mesure  10  a  13  //  de  long,  les  exemplaires  qui 
*  Laveran.  .Annales  de  I'hi.'itit.  Past.,  1908. 
X 
