413 
This  rapid  liberation  of  antimonic  oxide,  which,  as  is  well  known, 
IS  very  slowly  resorbed  by  the  tissues  and  causes  great  irritation,  may 
be  the  cause  of  abscess  formation  at  the  site  of  injection.  This 
disadvantage  of  abscess  formation  was  overcome  by  introducing  an 
organic  antimony  compound  of  a  similar  type  to  Atoxyl  into  the 
therapeutics  of  Trypanosomiasis,'^'  the  antimony  radical  being  linked 
on  to  the  aromatic  nucleus.  From  the  three  isomeric  arylstibinic 
acids  only  the  para  derivative  gave  satisfactory  results.  The  meta 
compound  was  far  less  stable,  as  it  partly  decomposed  on  standing 
into  antimonic  oxide  and  aniline.  The  ease  with  which  this 
compound  decomposes  may  be  held  responsible  for  the  occurrence  of 
abscesses  after  injection.  The  antimony  is  probably  too  quickly 
liberated  and  not  sufficiently  quickly  resorbed. 
The  mechanism  of  the  action  of  the  p-amino-phenyl-stibinic  acid 
is  similar  to  that  of  p-amino-phenyl-arsenic  acid  (Atoxyl).  It  is 
remarkable  on  comparing  the  action  of  sodium  antimonyl  tartrate  and 
of  sodium  p-amino-phenyl-stibinic  acid,  that  whereas  the  first  named 
compound  effects  a  disappearance  of  the  parasites  within  one  hour, 
the  latter  compound  produces  the  same  effect  only  after  the  lapse  of 
15-19  hours.  The  effect  stands  in  direct  proportion  to  the  rate  at 
which  antimony  is  set  free  from  the  drugs. 
RESISTANCE 
Thomas  and  Breinlf  observed  in  their  work  on  Atoxyl  in  experi¬ 
mental  trypanosomiasis,  that  in  a  horse  infected  with  T.  evansi,  the 
parasites  disappeared  from  the  blood  after  administration  of  Atox)  !. 
In  spite  of  continuation  of  the  treatment,  parasites  were  seen  again, 
and  ‘  were  twenty-five  to  a  field  on  the  fourth  day  after  the  dose  in 
the  last  week  but  one.  Two  doses  per  week  were  therefore 
commenced ;  this  kept  the  number  of  parasites  down,  so  that  one  to 
five  fields  was  the  highest  reached.’ 
Similar  observations  were  made  by  Mesnil  and  Nicolle,+  using- 
benzidine  colours  for  the  treatment  of  experimental  trypanosomiasis. 
*  J]reinl  and  Nierenstein.  Annals  of  Tropical  Medicine  and  Parasitology, 
\'ol.  II,  No.  5,  igog. 
t  Thomas  and  llreinl.  Liverpool  School  of  Tropical  Medicine,  Memoir  XVI, 
1905,  p.  65. 
I  Mesnil  and  Nicolle.  Annales  de  ITnstit.  Pasteur,  No.  XX,  p.  528,  1906. 
