THE  AMERICAN 
journal  or  :iti:ak 
SPECIFICITY  OF  DRUGS  FOR  PP^pSP: 
By  C.  G.  MacArthur  and  G.  D.  Cald' 
CY 
The  phosphatids  are  blamed  for  a  great  many  physiological 
changes.  Very  often  they  are  ascribed  these  special  functions  be- 
cause certain  other  tissue  constituents  have  been  shown  not  to  be 
involved,  more  often,  however,  because  of  their  resemblances  to 
ordinary  fats.  If  one  notes  the  complex  and  peculiar  composition 
of  the  phosphatids  it  will  be  evident  that  it  is  not  safe  to  rely  too 
much  on  the  physical  resemblances  to  fats  in  an  explanation  of  the 
physiological  part  the  phosphatids  play  in  the  selective  activities  of 
the  tissue  cells. 
In  this  investigation  an  attempt  was  made  to  see  if  there  was 
any  evidence  that  brain  lecithin  was  involved  in  the  specific  action 
of  brain  drugs,  and  that  heart  drugs  were  not  thus  related  to  brain 
lecithin  but  were  to  heart  lecithin.  There  is  some  evidence  now 
that  the  two  lecithins  as  prepared  for  this  investigation  are  at  least 
very  similar  in  chemical  constitution.2  If  the  two  are  identical  the 
drug  specificity  could  not  be  attributed  to  their  presence,  but  might 
be  to  a  difference  in  amount  or  to  a  peculiarity  in  their  position. 
It  is  necessary  to  keep  in  mind  the  fact  that  there  is  not  a  very 
large  amount  of  specificity  in  the  drugs  used  for  either  of  the  tissues 
studied.  In  general  there  is  only  a  difference  in  the  degree  of  effect 
produced  by  a  drug  on  the  various  tissues  of  the  body.  Then,  too, 
it  does  not  necessarily  follow  that  because  there  is  a  certain  pre- 
1  The  importance  of  the  work  here  reported  was  urged  by  the  late  Walde- 
mar  Koch.  He  was  largely  instrumental  in  getting  the  investigation  properly 
started.    C.  G.  M. 
2  J.  E.  Darrah  and  C.  G.  MacArthur,  Jour.  Am.  Chem.  Soc,  38,  922,  1916. 
C.  G.  MacArthur,  F.  G.  Norbury  and  W.  G.  Karr,  Jour.  Am.  Chem.  Soc,  39, 
768,  191 7, 
