644  United  States  Pharmacopoeial  Revision.  { ^^p/ember^'Y/lo: 
In  lieu  of  a  standard  extract  furnished  by  some  central  authority 
such  as  the  U.  S.  Hygienic  Laboratory,  what  is  the  use  of  running  an 
assay  each  time  on  a  standard  preparation  when  the  strength  of  the 
standard  is  obtained  by  adjusting  a  preparation  until  it  is  of  such 
strength  that  0.03  Mil.  of  the  fluid  extract  per  kilo  will  produce  in- 
coordination. 
Why  not  adopt  0.03  Mil.  per  kilo  as  a  standard  and  calculate  the 
strength  of  the  unknown  by  comparing  the  dose  of  it  necessary  to 
produce  incoordination  with  the  above  0.03  Mil.  per  kilo  instead  of 
the  amount  of  the  standard  necessary  to  produce  the  same  effects? 
If  the  standard  is  of  proper  strength,  will  it  not  require  exactly 
0.03  Mil.  per  kilo?  The  only  object  for  assaying  the  standard  prep- 
aration each  time  would  be  to  avoid  errors  due  to  the  variation  in 
the  susceptibility  of  dogs.  The  use  of  a  standard  preparation, 
unless  supplied  by  some  central  authority,  will  not  avoid  this  error 
because  the  standard  preparation  is  adjusted  to  the  above  standard 
dose  and  not  to  standard  dogs.  Are  you  not  just  as  liable  to  have 
dogs  which  are  over  or  under  normal  susceptibility  when  you  adjust 
the  standard  as  when  assaying  an  unknown,  thus  making  the  standard 
slightly  over  or  under  strength?  If  so,  by  adopting  the  longer 
process  of  assaying  both  standard  and  unknown  each  time,  the 
error  due  to  variation  in  susceptibility  is  only  increased  because 
you  adopt  as  a  standard  preparation  one  which  may  be  slightly 
over  or  under  strength  and  then  adjust  all  subsequent  preparations 
to  this,  thus  making  the  same  error  in  all,  whereas  by  the  shorter 
method  of  adopting  a  definite  dose  as  standard  we  only  have  an 
occasional  preparation  a  little  off  strength,  due  to  an  over  or  under 
susceptibility  of  the  dogs  used  on  that  particular  assay. 
Due  to  the  variation  in  susceptibility  of  different  dogs,  the 
method  must  essentially  be  comparative  and  not  absolute.  This 
necessitates  the  adoption  of  an  arbitrary  standard  with  which  the 
activity  of  the  unknown  can  be  compared.  The  U.  S.  P.  method 
would,  therefore,  be  very  satisfactory  had  the  Committee  only  gone 
a  step  farther  and,  as  suggested  by  Pearson,^  made  arrangements  for 
supplying  manufacturers  with  a  suitable  standard  with  which  to 
compare  the  activity  of  their  preparations.  Until  such  a  standard 
is  supplied,  however,  it  is  only  a  waste  of  time  to  run  an  assay  on  a 
standard  preparation,  which  the  manufacturer  has  prepared  himself; 
each  time  an  unknown  sample  is  tested. 
1  Pearson,  This  JournaIv,  Nov.,  191 6. 
