io6  Biological  Standardization  of  Drugs.    {^\tZ[  i<i\T'' 
on  by  the  clinician  and  which  may  be  used  as  a  basis  for  dosage 
as  safely  as  if  assays  were  carried  out  on  guinea-pigs,  rabbits, 
cats,  or  dogs  and  so  far  as  the  evidences  of  accuracy  and  totality 
of  action  go  far  more  safely  than '  if  carried  out  by  estimating 
the  single  active  constituent  digitoxin  or  digitalin  by  chemical 
means.  Assays,  as  is  to  be  noted  by  the  above  summary,  may  be 
made  using  frogs  (possibly  also  other  animals)  which  will  give 
an  estimate  of  the  amount  of  glucosides  in  a  solution  to  within  a 
few  (i  to  lo)  per  cent,  of  absolute  accuracy. 
In  all  cases  in  therapeutics  the  unknown  factors  of  absorption, 
elimination,  and  susceptibility  will  persist  in  spite  of  all  attempts 
at  assaying  the  preparations  of  the  digitalis  group.  But  these 
factors  would  also  exist  in  like  degree  as  long  as  several  differently 
active  bodies  and  resinous  substances  are  to  be  reckoned  with  even 
if  absolute  chemical  assays  of  not  one  but  all  the  active  glucosides 
of  the  group  were  possible.  The  frog  method  of  assay  gives  all 
any  assay  method  can  possibly  give,  that  is,  a  definite  index  of 
the  amount  of  active  substances,  and  what  is  especially  important 
an  index  of  the  activity  of  all  substances  in  the  preparation  which 
act  upon  the  heart. 
Certain  factors  regarding  variation  in  reaction  of  frogs  to  the 
digitalis  group  of  glucosides,  or  to  other  poisons,  are  of  little 
importance  aside  from  increasing  to  a  very  slight  degree  the  com- 
plexity of  the  assay  process.  The  whole  question  resolves  itself 
into  a  matter  of  using  a  digitalis  preparation  of  known  activity 
and  keeping  quality  (and  for  this  purpose  crystallized  digitoxin 
or  ouabain  is  suggested)  to  standardize  the  frogs  at  the  same  time 
that  the  unknown  is  assayed.  In  this  way  accurate  results  max 
be  obtained  without  reference  to  season,  age,  sex,  temperature 
conditions,  or  species  of  frogs  used. 
I  have  purposely  discussed  at  some  length  the  frog-heart  method 
as  proposed  by  Famulener  and  Lyons  and  it  may  be  regarded  some- 
what as  a  personal  matter  with  me  since  I  use  it  that  I  should 
give  it  so  much  time.  T  have  tried  not  tO'  make  it  so  and  have 
approved  of  it  because  in  my  best  judgment  it  was  based  on  per- 
fectly sound  physiological  facts  as  well  as  experimental  evidence 
for,  excepting  Hatcher's  cat  method,  all  these  methods  have  been 
reviewed  after  personal  investigation  and  the  whole  matter  con- 
sidered as  impartially  as  possible  previous  to  its  adoption.  It  is  a 
fact,  however,  that  long  acquaintance  with  a  particular  method 
