Am.  jour,  pharm.)        Bioloqical  Standardisation. 
February,  1917-    3  0 
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This  method  is  subject  to  the  same  variable  factors  as  the  M.  L. 
D.  method,  namely,  temperature,  season,  different  species  of  frogs 
and  their  individual  susceptibility  with  the  additional  disadvantage 
that  absorption  becomes  a  more  serious  factor  on  account  of  the 
shorter  time  of  action.  The  apparent  advantages — fewer  frogs  and 
shorter  time — are  under  some  conditions  real  disadvantages  because 
in  case  of  delayed  absorption  a  frog's  heart  will  be  found  beating  in 
1  hour,  even  when  dosed  with  the  M.  S.  D.  while  the  M.  L.  D.  would 
not  be  appreciably  affected.  Another  important  point  in  connection 
with  the  end  point  in  the  M.  S.  D.  method  is  the  effect  of  pithing 
the  frog  and  laying  bare  its  heart.  Is  it  reasonable  to  suppose  that 
this  has  no  influence  on  the  condition  of  the  heart?  Whatever  this 
influence  is  it  can  scarcely  be  inferred  that  this  is  an  invariable  and 
uniform  effect.  The  method  therefore  introduces  one  more  factor, 
the  effect  of  which  tends  towards  variability  rather  than  in  the  di- 
rection of  increasing  accuracy. 
After  an  extended  series  of  tests  Hamilton  &  Rowe  (5)  found 
that  the  M.  S.  D.  of  digitalis  is  less  than  the  M.  L.  D.,  showing  that 
an  early  paralysis  of  the  heart  occurs  which  may  be  the  cause  of  the 
observed  indefinite  end  point.  This  paralysis  seems  to  have  no  uni- 
form relationship  to  the  M.  L.  D.  since  in  some  cases  the  M.  L.  D. 
and  M.  S.  D.  were  identical,  while  an  average  of  14  experiments 
showed  the  latter  to  exceed  the  former  by  22  per  cent,  in  the  case 
of  fluid  extracts,  and  36  per  cent,  in  the  case  of  tinctures,  the  latter 
being  an  average  of  12  tests.  In  one  assay  of  a  tincture  by  both 
methods  the  M.  L.  D.  exceeded  the  M.  S.  D.  by  60  per  cent. 
The  conclusion  of  Edmunds  and  Hale  that  choice  between  the 
two  methods  is  largely  one  of  convenience  seems  unwarranted.  The 
most  uniform  end  point,  and  the  most  logical,  is  that  where  the 
sample  of  a  digitalis  preparation  has  an  opportunity  to  complete 
its  cycle  of  effects  and  to  be  measured  by  the  size  of  the  minimum 
dose  which  causes  death  of  the  frog  with  heart  in  systole.  Any 
other  stage  in  this  cycle  is  more  variable  and  therefore  less  accurate 
as  an  end  point  for  the  reaction. 
The  standard,  ouabain,  adopted  by  the  committee  for  comparison 
in  measuring  the  activity  of  the  digitalis  series  of  heart  tonics  is  also 
open  to  criticism  because  it  is  obtained  from  a  non-official  strophan- 
tus seed  and  because  different  lots  are  not  uniform  in  composition. 
While  it  is  true  that  the  standard,  in  physiological  assaying,  is 
merely  to  measure  the  resistance  of  the  frogs,  this  resistance  is  of 
