AmMa?cUh,' iP9i3rm' }    Standardization  of  Digitalis  Bodies,  121 
be  preferred  on  account  of  the  greater  similarity  between  these  and 
man;  this  being  especially  characteristic  of  the  cat  method. 
6.  The  results  of  the  frog  methods  cannot  be  transferred  to  man, 
not  even  the  results  of  tests  of  the  relative  toxicity  of  different 
closely  allied  bodies.  The  standing  of  the  guineapig  method  on 
this  point  is  much  the  same.  The  cat  method  does  give  results  which 
are  directly  transferable  to  man,  both  as  regards  actual  toxicity  of 
a  single  drug  and  the  relative  activity  of  different  members  of  the 
series. 
7.  It  is  not  possible  to  compare  different  members  of  the  digi- 
talis group  by  the  guineapig  or  frog  methods,  owing,  principally,  to 
the  great  influence  of  absorption  on  the  results  obtained  by  these 
methods.  By  the  cat  method  comparisons  can  be  made  of  the 
activity  of  any  two  or  more  members  of  the  series  wholly  regardless 
of  their  differences  in  absorbability. 
8.  The  frog  and  guineapig  methods  are  limited  in  their  range  of 
applicability  by  factors  of  absorption,  alcoholic  content,  etc.  This 
is  not  the  case  with  the  cat  method,  which  has  a  wide  range  of 
applicability. 
9.  All  of  the  methods  are  subject  to  the  influence  of  adventitious 
factors,  the  guineapig  method  being  the  most  affected,  the  frog  the 
next,  and  the  cat  the  least.  In  the  latter  animal  the  use  of  a  short 
series  of  tests  practically  nullifies  the  influence  of  the  adventitious 
factors. 
10.  The  frog  and  guineapig  methods  show  moderate  to  great 
differences  in  the  evaluations  made  for  the  same  specimen  at 
different  times,  and  hence  cannot  be  trusted  to  give  correct  in- 
formation concerning  the  presence  or  absence  of  deterioration  in  a 
given  preparation.  The  cat  method  gives  concordant  results  with 
permanent  preparations  tested  at  long  intervals  and  shows  the 
presence  of  deterioration  with  certainty. 
11.  It  is  possible  to  obtain  reasonably  accurate  results  with  any 
of  the  methods — to  within  ten  per  cent. — but  the  frog  method 
probably  gives  the  least  range  of  variation  in  the  case  of  a  pure 
principle,  provided  that  it  is  soluble  in  water. 
12.  The  cat  method  is  the  only  one  which  affords  any  evidence 
of  the  relative  therapeutic  value  of  the  different  members  of  the 
digitalis  group. 
CONCLUSIONS. 
There  is  no  perfect  or  ideal  method  of  standardizing  the  mem- 
bers of  the  digitalis  group  biologically. 
