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The  formation  of  oxy-carb-amino-phenyl-arsenic  acid  can  be 
explained  in  the  following  way.  The  organism  introduces  on 
oxidation  an  OH  group  in  the  o-position  to  the  amido  group,  and 
thus  forms  p-amino  m-oxy-phenyl-arsenic  acid  (Formula  VI).  This 
oxidation  is  then  followed  (based  on  the  analogy  of  toluidme)  by  an 
intermediate  acetylation  of  p-amino-  m-oxy-phenyl-arsenic  acid  in 
the  organism  (Formula  VII).  The  acetyl  chain  is  oxidized,  and  forms 
oxy-carbonyl  arsenic  acid  (Formula  III). 
On  considering  the  foregoing  experiments  and  results,  it  becomes 
possible  to  divide  the  action  of  Atoxyl  in  the  organism  into  four 
phases. 
I.  After  injection  of  Atoxyl,  a  comparatively  small  amount 
combines  through  the  amino  group  with  the  serum  jiroteins  and 
forms  ‘  Atoxyl-serum  ’ ;  the  greater  part  is  secreted  in  the  urine, 
partly  unchanged  as  p-ami no-phenyl-arsenic  acid,  partly  oxidised  in 
the  form  of  p-oxy-phenyl-arsenic  acid  and  oxycarb-amino-phenyl- 
arsenic  acid,  and  partly  as  free  inorganic  arsenic. 
II.  From  the  Atoxyl  serum,  arsenic  is  set  free  through  an 
oxidation  process,  caused  by  the  oxidative  ferments  present,  and 
probably  also  by  the  trypanosomes,  whereby  the  aromatic  nucleus  is 
destroyed. 
III.  At  the  same  time  a  reduction  process  takes  place  in  the 
intestines,  whereby  the  Atoxyl  molecule  is  reduced  to  aniline  and 
arsenious  acid. 
IV.  The  arsenic  which  is  formed  through  oxidation  acts  in  statu 
nascendi  on  the  trypanosomes. 
As  has  been  pointed  out  before,  the  action  of  Atoxyl  can  be 
Compared  to  that  of  a  dye.’^'  The  amino  group  plays  the  role  of  a 
*  Nierenstein.  Annals  of  Tropical  Medicine  and  Parasitology,  Vol.  II,  No.  3, 
p.  249,  1908.  ^ 
