401 
in  order  to  imitate  as  far  as  possible,  in  vitro,  the  changes  whicli 
Atoxyl  undergoes  in  the  organism,  an  ‘  Atoxyl-serum  ’  was  prepared 
by  mixing  a  solution  of  Atoxyl  with  serum  and  dialysing  out  the 
excess  of  Atoxyl  which  had  not  combined  with  the  serum  proteins 
through  the  amino  group.  On  the  addition  of  liver  emulsion  or 
to  this  ‘  Atoxyl-serum  ’  inorganic  arsenic  was  set  free. 
Nierenstein’s*  research  on  the  mode  of  elimination  of  Atoxyl  in 
the  urine  confirms  our  conception  that  Atoxyl  mainly  undergoes 
oxidation  in  the  organism.  After  injecting  the  drug  into  a  horse,  it 
was  recovered  in  the  urine  in  the  form  of  p-amino-phenyl-arsenic 
acid  (Formula  I),  p-oxy-pheny  1-arsenic  acid  (Formula  II),  and 
oxy-carb-amino-phenyl  arsenic  acid  (Formula  III). 
It  is  obvious  that  the  formation  of  the  compounds  II  and  III 
from  I  (the  mother  substance  of  Atoxyl)  can  only  be  explained  through 
an  oxidation  process  in  the  organism. 
The  formation  of  p-oxy-phenyl-arsenic  acid  (Formula  II)  from 
p-amino-phenyl-arsenic  acid  is  brought  about  through  a  replacement 
of  the  amino  group  by  an  HO  group,  and  is  similar  to  the  formation 
of  p-amino-phenol  (Formula  IV)  after  injection  of  p-amino-anihne 
(Formula  V). 
This  oxidation  process  enables  the  organism  to  eliminate  aniline 
and  Atoxyl  in  a  less  toxic  form  as  the  sulphuric  or  glycuronic 
derivatives. 
*  Nierenstein.  Zeit.  f.  Immunitatsforschung,  Bd.  II,  No.  4,  1909. 
