ADe'cJe?"benbi™'}       Valuation  of  Drugs  and  Foods.  591 
their  products  dissociate  electrolytically.  Here  the  H  ions  may 
account  for  much  of  the  toxic  action.  In  the  cresols  and  mono- 
nitrophenols,  electrolytic  dissociation  seems  to  exert  a  pronounced 
influence.  Some  phenols  are  comparatively  weak  in  this  integrity, 
but  quickly  change  to  substances  containing  constituents  even  more 
fatal  than  H  ions.  Pyrocatechol,  and  especially  hydroquinone,  are 
of  this  class. 
"  Certain  radicles  seem  to  have  specific  properties  when  introduced 
into  the  molecule,  modifying  the  toxic  value.  The  number  of 
hydroxyl  groups  (OH)  present  seems  to  have  little  influence  on  the 
toxic  action  of  the  phenols,  as  in  the  series  benzophenol  (OH), 
resorcinol  (2OH)  and  phloroglucin  (3OH).  The  introduction  of  the 
methyl  group  (CH3)  into  the  benzine  nucleus  increases  the  toxicity 
to  a  considerable  but  rather  variable  degree,  as  in  the  cresols,  less 
plainly  in  orcinol.  The  introduction  of  the  isopropyl  group 
[ — CH3(CH3)2]  into  the  cresols  increases  the  toxic  value  of  these 
substances,  as  carvacrol  and  thymol.  The  presence  of  one  or  more 
nitro  groups  (N02)  increases  the  toxic  action  to  a  great  degree  ;  mono- 
and  tri-nitrophenols.  An  increase  in  the  number  of  the  N02  groups 
present  does  not  seem  to  increase  the  toxic  action.  When  the  H  of  an 
OH  group  is  replaced  by  a  (CH3)  group,  little  influence  seems  to  be 
exerted  on  the  toxic  action,  e.  g.y  anisol  and  guaiacol.  The  carboxyl 
group  (COOH)  brings  with  it  a  degree  of  toxicity  corresponding 
directly  to  the  degree  of  dissociation  and  the  number  of  H  ions  it 
affords ;  salicylic  acid," 
It  is  apparent,  from  this  brief  review  of  some  of  the  more  im- 
portant points  of  the  work  on  the  application  of  the  theory  of  the 
dissociation  of  electrolytes  to  explain  the  toxic  action  of  various 
substances  on  living  organisms,  that  it  has  not  only  an  important 
scientific  interest,  but  one  which  is  likely  to  yield  in  a  practical 
manner  some  very  important  results.  For  instance,  Kahlenberg 
and  True  recognized  from  the  beginning  the  adequacy  of  this 
theory  to  explain  the  action  of  antiseptics,  and  later  Paul  and 
Kroenig1  verified  these  views.  Certain  plants,  however,  show  a 
marked  sensitiveness  to  certain  substances  ;  for  instance,  spirogyra 
is  far  more  sensitive  to  the  heavy  metals,  but  is  more  tolerant 
towards  acids  than  the  seeds  of  Lupinus  albus.     On  the  other 
1  Zeitschr.  f.  physik.  Chemie,  1896,  p.  414. 
