AjanuTryPih9i4m'}  Ehrlich' s  Chemotherapy.  29 
and  seriously  harmful  effects  to  the  patients  were,  however,  the 
consequence  of  this  treatment,  but  the  parasiticidal  properties  of 
this  compound  were  so  marked  that  Ehrlich  turned  his  attention  to 
it,  in  an  attempt  to  so  modify  its  effects  upon  the  animal  organism 
which  was  harboring  the  parasites,  that  its  curative  power  might  be 
made  available. 
The  task  was  by  no  means  a  simple  one.  He  first  established  the 
composition  of  the  atoxyl  as  a  para-amido-phenyl  arsenic  acid.  The 
vast  amount  of  work  already  done  with  the  dye-stuff  indicated  certain 
lines  of  probable  success,  which,  nevertheless,  was  only  attained  on 
the  synthesis  of  the  six  hundred  and  sixth  organic  compound  by 
Ehrlich  and  Kata,  sometimes  known  as  "  606,"  and  now  designated 
salvarsan.  Chemically  it  is  dioxy-diamido-arseno-benzol,  in  which 
arsenic  is  associated  with  structural  groups  akin  to  those  found  in 
the  dye-stuffs.  A  later  preparation  "  914,"  known  as  neo-salvarsan, 
is  said  to  be  a  combination  of  a  salvarsan  with  sodium  formaldehyde 
sulphoxalate,  which  is  designed  to  overcome  a  certain  difficulty  in 
administration  of  the  salvarsan,  due  to  acidity  of  its  solutions. 
Ehrlich  assumes  that  the  parasite  of  syphilis,  the  spirochete, 
possesses  among  others,  arsenio-receptors,  and  that  through  the 
combination  with  this  arsenic  compound  the  parasite  is  poisoned  and 
dies.  Ehrlich  claims  that  in  more  than  twelve  thousand  cases  in 
which  this  drug  has  been  administered  by  him,  no  single  case  of 
poisoning  has  resulted.  The  administration  of  the  drug,  which  is 
intravenous,  or  intramuscular,  requires,  however,  considerable  skill 
and  care.  The  treatment  with  salvarsan  is  often  combined  with 
that  of  mercury.  There  seems  to  be  no  doubt  that  this  preparation 
exerts  a  specific  and  destructive  action  upon  the  spirochete,  and  has 
already  resulted  in  the  alleviation  of  an  enormous  amount  of  suf- 
fering (often  hereditary  and  undeserved)  from  this  dreadful 
scourge.  It  is  still  too  early  to  make  final  statements  as  to  the  per- 
manence of  the  cures  affected  although  there  is  much  reason  for 
hopefulness.  It  should,  however,  be  noted  that  this  chemothera- 
peutic  treatment,  unlike  the  anti-toxin  treatment  for  certain  other 
diseases,  does  not  at  all  produce  immunity  from  later  infection  from 
the  same  disease.  Indeed,  there  is  some  evidence  to  show  that  cases 
of  re-infection  are  distinctly  harder  to  treat  successfully  than  those 
of  initial  infection.  The  cure  of  advanced  cases  of  the  disease  natu- 
rally, presents  greater  difficulties,  because  of  secondary  disturbances 
of  the  vital  organs,  but  many  of  these  have  been  materially  alleviated. 
