AmkSchr;iP9i3rm'}    Standardization  of  Digitalis  Bodies.  107 
determinations  lies  in  the  variations  in  reaction  between  different 
batches  of  frogs  and  will  be  discussed  later. 
The  extent  to  which  the  guineapig  method  may  be  expected  to 
provide  a  similar  means  of  comparison  cannot  as  yet  be  definitely 
stated,  but  certain  results  obtained  by  Haskell  would  seem  to  show 
that  seasonal  variations  in  these  animals  are  such  that  comparisons 
cannot  be  drawn  between  tests  made  at  different  times  of  year.  In 
a  period  of  five  months  a  given  specimen  of  ouabain  was  tested 
on  these  animals  and  the  activity  found  varied  from  0.000,000,28 
to  0.000,000,52  gram  per  gram  of  pig.  Such  enormous  variations 
are  absolutely  unknown  in  cats,  and  have  never  been  reported  in 
frogs,  by  whatever  method  tested. 
The  method  should  be  as  little  subject  to  the  influence  of  ad- 
ventitious factors  as  possible.  All,  or  nearly  all,  are  agreed  that 
frogs  are  very  susceptible  to  the  influence,  of  such  factors,  and  the 
warmest  advocates  of  the  frog  as  a  test  animal  admit  that  size,  sex, 
season,  temperature,  moisture,  presence  of  eggs,  region  from  which 
obtained,  etc.,  may  materially  affect  the  reaction  of  the  animal  to 
the  heart  tonic  group.  Baker 12  has  made  a  study  of  many  of  these 
factors  and  states  that :  "  The  results  emphasize  the  necessity  of 
using  a  preparation  to  standardize  the  frogs  for  each  series  of  as- 
says." This  necessity  is  becoming  generally  recognized  by  most  of 
the  workers  in  this  field  and  such  standardization,  introduces  certain 
factors  of  great  detriment  to  the  general  applicability  of  the  method 
to  the  entire  digitalis  series.    This  will  be  considered  separately. 
In  addition  to  the  factors  already  mentioned  as  influencing  the 
results  on  frogs  it  is  to  be  recalled  that  dilution  of  the  drug  has  a1 
marked  influence  on  the  result  obtained.  Hale  emphasizes  the  im- 
portance of  maintaining  the  concentration  of  the  specimen  to  be 
tested  within  such  limits  that  the  fatal  dose  for  a  frog  will  be  con- 
tained in  one  cubic  centimeter  of  the  solution.  Focke  13  states  that 
the  degree  of  dilution  in  the  case  of  the  strophanthus  preparations  is 
very  important,  for,  "  a  higher  dilution  results  in  a  higher  reaction 
value." 
Guineapigs  seem  to  be  quite  as  susceptible  to  the  influence  of 
extraneous  factors  as  are  frogs.  Thus,  Vanderkleed  found  that 
these  animals  are  very  susceptible  to  changes  in  diet  and  ventilation, 
and  that  these  factors  very  quickly  impair  the  health  of  the  pigs  or 
12  A.  J.  PHARM.  ;   1912;  84;  p.  247. 
13  Arch,  der  Pharm.  1910,  248,  p.  345. 
