4ig 
Similar  observations  have  been  made  by  Uhlenhuth  and  Woithe 
with  regard  to  a  dog  infected  with  T.  eqiiiperdinn,  subsequently 
treated  with  Atoxyl. 
In  animals  infected  with  7 .  gambiense,  the  average  relapsing  time 
after  discontinuation  of  treatment,  as  previously  remarked,  lies 
between  50  and  60  days ;  therefore,  observation  over  a  very 
prolonged  period  is  necessary  before  considering  an  animal  cured. 
Occasionally,  even  in  an  untreated  monkey  during  an  infection  with 
7.  gambiense,  longer  intervals  may  occur,  during  which  parasites,  in 
spite  of  careful  daily  examination,  cannot  be  detected,  and  only  inter¬ 
current  diseases  which  lower  the  vitality  of  the  infected  organism 
cause  a  leappearance  of  the  parasites.  Two  of  our  infected  monkeys 
succumbed  to  an  intercurrent  pneumonia  and  pleurisy.  In  the  blood 
of  the  animals,  although  parasites  had  not  been  seen  for  41  days, 
trypanosomes  in  scanty  number  reappeared  on  the  day  before  death. 
A  third  monkey,  a  very  large  Cercopiihecus  callitrichus,  had 
seemingly  recovered  easily  from  an  infection  with  T .  gambiense.  Its 
weight  increased,  the  blood  count  was  normal,  and  we  were  inclined  to 
assume  a  natural  cure  in  this  animal.  Subinoculations  made  upon 
rats  proved  negative.  After  a  negative  interval  of  74  days  the  animal 
suddenly  became  markedly  ill.  This  was  due  to  an  abscess  of  the 
gum,  which  spread  in  a  very  short  time  along  the  upper  jaw  and  led  to 
the  death  of  the  animal  at  the  end  of  three  days.  On  the  day  previous 
to  death,  trypanosomes  were  seen  in  the  peripheral  blood  in  very 
scanty  number  (i  to  3  coverslip  preparations).  At  death  only  one 
parasite  could  be  found  in  three  coverslip  preparations.  Subinocu¬ 
lations  into  two  guinea-pigs  and  two  rats  were  made  after  death  with 
fairly  large  quantities  of  blood.  One  guinea-pig  inoculated  intra- 
peritoneally  succumbed  to  a  purulent  peritonitis ;  the  second 
guinea-pig,  inoculated  subcutaneously,  developed  an  abscess  at  the 
site  of  inoculation,  but  became  infected  after  an  incubation  period  of 
15  days.  Both  rats,  inoculated  subcutaneously,  developed  a  typical 
infection  of  T .  gambiense,  and  succumbed  in  due  time  to  the  disease. 
These  observations,  together  with  many  others  made  during  our 
experimental  work,  point  to  the  assumption  that  the  general  condition 
of  experimental  animals  influences  to  a  large  extent  the  results 
obtained  in  therapeutical  experiments. 
