4o8 
and  within  three  days  the  animal  was  totally  blind.  As  no  recovery 
of  vision  took  place,  the  animal  was  killed  with  the  intention  of 
examining  the  pathological  lesions  of  the  eye. 
One  Macaciis  rhesiLs  was  inoculated  with  T.  ganibiense.  Treat¬ 
ment  was  begun  after  the  second  natural  relapse.  After  one 
injection  of  o  i  gm.  of  Orsudan  the  parasites  promptly  disappeared. 
Thirty-five  days  afterwards  a  second  injection  of  o‘i  gm.  of 
Orsudan  was  given.  During  the  following  day  symptoms  of  severe 
arsenic  poisoning  set  in,  and  the  animal  became  totally  blind  six  days 
after  the  injection.  This  monkey  is  still  alive  thirteen  months  after 
the  inoculation.  He  is  absolutely  blind,  and  no  visible  changes  can 
be  noticed  in  his  eyes. 
The  foregoing  experiments  lead  to  the  conclusion  that  Orsudan 
as  a  trypanocide  is,  for  T.  gambiense  and  T.  equiperdum  in  experi¬ 
mental  animals,  nearly  equal  to  that  of  Atoxyl. 
As  with  Atoxyl,  only  in  a  very  small  percentage  of  our  experi¬ 
ments  have  we  been  able  to  prevent  relapses.  On  the  other  hand, 
Orsudan  is  certainly  very  toxic  indeed,  as  our  experiments  in  monkeys 
show  ;  out  of  four  animals  treated,  two  cases  of  blindness  and  one 
death  from  typical  arsenic  poisoning  occurred.  The  higher  toxicity, 
when  compared  with  Atoxyl,  may  be  explained  on  the  hypothesis  that 
Orsudan  combines  to  a  larger  extent  with  the  tissue  than  Atoxyl, 
owing  to  the  fact  that  CH^  group  is  oxidised  to  COOH,  and,  there¬ 
fore,  more  arsenic  combines  and  is  afterwards  set  free  in  the  orp’anism.'*' 
In  a  few  of  our  experiments  on  rats,  haemoglobinuria,  the  result 
of  haemolysis,  was  noticed.  This  may  be  due  to  the  well-known  fact 
that  toluidine  derivatives  are  more  powerful  haemolytic  agents  than 
aniline  derivatives. 
D.  Derivatives  of  Orsudan. 
I.  Sodium  3 -methyl  4-hydroxy-phenyl-arsenate. 
*  Lately  we  have  had  an  opportunity  of  testing  a  new  sample  of  Orsudan.  Two 
successive  injections  of  0'2  gr.  into  a  monkey  did  not  give  rise  to  any  symptoms  of  arsenical 
poisoning. 
