Am.  Jour.  Pharm. 
May,  1911. 
Standardisation  of  Digitalis. 
203 
the  smallest  dose  which  proved  fatal  in  the  first  case,  and  if  the 
majority  of  these  are  dead  at  the  end  of  12  hours,  this  dose  is 
accepted  as  the  m.  1.  d. 
Focke's  ^  experiments  seem  to  have  been  carried  out  on  Rana 
femporaria.  The  animals  are  fastened  to  a  board  and  the  heart  is 
exposed  with  avoidance  of  hemorrhage.  The  drug,  in  the  form  of 
an  infusion,  is  injected  into  the  femoral  lymph  sacs,  and  the  time 
noted  before  systolic  stoppage  of  the  heart. 
A  factor  V  is  then  determined  from  the  weight  of  the  frog, 
size  of  the  dose,  and  lapse  of  time  before  systolic  stoppage  of  the 
heart. 
The  one-hour  frog  heart  method  was  originated  by  Cushny  *  and 
is  now  much  used  by  his  pupils,  Edmunds  and  Hale.  (The  method 
proposed  by  Fraenkel  ^  in  1902  differs  from  this  in  several  important 
details.)  It  resembles  Houghton's  method  in  that  the  frogs  are 
injected  in  series  and  comparison  is  made  with  another  series  in- 
jected with  a  standard  preparation.  At  the  expiration  of  exactly  60 
minutes,  however,  the  animals  are  pithed  and  the  hearts  exposed. 
When  just  the  proper  dose  or  an  amount  slightly  in  excess  has  been 
injected,  the  heart  presents  a  characteristic  picture ;  the  auricles 
purple  and  distended;  the  ventricle  white,  motionless,  and  con- 
tracted. 
In  1908,  Reed  revived  the  guinea-pig  method  for  determining 
the  strength  of  preparations  of  the  "  heart  tonics."  Laborde  and 
Duquesnel,^^  in  1884,  were  apparently  the  first  to  use  the  guinea-pig 
in  such  tests,  their  investigations  dealing  with  two  samples  of 
"  digitalin/'  the  solutions  of  the  drug  being  injected  subcutaneously 
or  intramuscularly.  In  1888,  Gley  ^  compared  the  toxicity  of  oubain 
and  strophanthin,  using  guinea-pigs  and  other  animals.  When 
Houghton,^^  in  1898,  published  his  method  for  the  assay  of 
strophanthus,  he  stated  that  he  had  employed  guinea-pigs,  as  well 
as  frogs  and  other  animals,  upon  which  to  perform  experiments. 
Reed  believes  that  frogs  are  unsuitable  animals  tO'  employ  in 
these  tests,  because  they  vary  in  their  resistance  to  the  drug  accord- 
ing to  season,  species,  and  weight ;  while  the  guinea-pig  "  does  not 
appear  to  offer  so  wide  a  variation."  In  the  same  year,  Crawford  ^ 
pointed  out  the  unreliability  of  frogs,  their  powers  of  resistance 
depending  upon  season,  sex,  and  room  temperature.  He  considers 
that :  "  Dr.  Reed,  of  Philadelphia,  has  made  an  important  advance 
by  using  guinea-pigs,  animals  which  are  more  resistant  to  injury." 
