AFe'braa^y  *m£' }     Standardisation  of  Heart  Tonics.  65 
frogs.  As  this  is  usually  inconvenient,  these  observations  were 
made  after  one  hour,  two  hours,  six  hours,  or  twenty-four  hours. 
Some  workers  began  to  pith  the  frog  at  the  end  of  one  hour  and 
make  a  direct  examination  of  the  condition  of  the  heart,  for  it  was 
found  that  sometimes  frogs  would  be  apparently  normal  yet  their 
hearts  had  been  stopped  by  the  drug. 
Dr.  Hale  14  observed  that  more  concordant  results  were  obtained 
when  the  frogs  were  kept  at  the  uniform  temperature  of  22 0  C.  It 
would  neither  be  interesting  nor  instructive  to  relate  the  various  modi- 
fications that  have  been  proposed  for  the  Houghton  method. 
Edmunds  and  Hale,15  Edmunds  and  Cushny,16  and  Focke  17  have 
specified  various  conditions  under  which  the  "  frog  test "  is  to  be 
made,  but  none  of  these  methods  make  any  provision  to1  standardise 
the  frogs  that  are  used. 
It  is  known  that  variety,  weight,  sex,  season,  and  temperature 
affect  the  resistance  of  frogs  and  hence  it  is  possible  to>  obtain  different 
results  with  different  lots  of  frogs.  In  order  to  eliminate  these  factors 
of  unknown  significance  in  any  particular  case,  Houghton  and 
Hamilton  have  suggested  that  a  standard  be  used  in  testing  the 
resistance  of  every  lot  of  frogs,  at  the  time  the  test  is  made.  Upon 
these  data  "  The  Heart  Tonic  Unit  " 18  is  computed  in  every  case. 
The  standard  they  propose  to  use  is  crystalline  Strophanthin 
which  is  prepared  from  an  authentic  specimen  of  the  official  drug, 
Strophanthus  Komibe,  and  has  been  studied  in  detail  by  Braun  and 
Closson.19  The  outline  of  the  present  method  as  modified  by  Hough- 
ton is  as  follows : 
Frogs  should  all  be  of  same  species,  a  convenient  variety  is  the 
Rana  Pipiens.  They  should  all  be  of  weights  between  15  and  35  gm. 
and  the  weights  should  not  vary  more  than  25  per  cent,  in  any  one 
assay.  Before  being  used  the  frogs  may  be  kept  in  any  convenient 
place  where  the  water  can  be  frequently  changed  and  kept  at  a  tem- 
perature of  about  220  C.  During  the  test  the  frogs  can  advan- 
tageously be  kept  in  wire  cages  with  sheet  iron  bottoms,  standing 
in  trays  of  running  water,  but  the  depth  of  water  in  the  cages  should 
not  exceed  one-half  an  inch.  Scales  for  weighing  the  frogs  should  be 
accurate  within  0.5  gm.  The  necessary  apparatus  consists  of  volu- 
metric flasks,  cylinders,  graduated  pipettes  and  a  1  c.c.  pipette 
graduated  in  hundredths  of  a  cubic  centimetre  and  fitted  with  a  hypo- 
dermic needle  or  drawn  out  into  a  fine  point  for  injecting. 
