ANovemberPhi9ri9  ^  ^^an(^ar^za^on  °f  Digitalis  Preparations.  721 
of  digitalis — it  is  of  great  importance  that  attention  should  be  drawn 
to  their  standardization. 
Many  methods  have  been  put  forward  within  the  last  few  years, 
but  none  are  entirely  satisfactory  when  taken  alone. 
The  favorite  method  of  standardization  has  been  by  the  Min- 
imum Lethal  Dose  method — that  is,  the  amount  (calculated  pej  100 
Gms.  body  weight)  which,  injected  into  the  lymph  sac  of  the  frog,  is 
just  sufficient  to  kill. 
Different  physiologists  place  different  time  limits  on  this  experi- 
ment— some  two  hours,  four  hours,  six  hours,  etc.  A  few  hours 
after  injection  the  frogs  become  very  lethargic,  and  it  is  extremely 
difficult  to  differentiate  with  any  degree  of  accuracy  between  slight 
reflexes  and  total  death.  In  several  cases  I  have  known  frogs  from 
which  no  reflex  could  be  obtained  at  the  end  of  the  fourth  hour,  re- 
cover during  the  night. 
Again  the  strength  of  tinctures  containing  excess  of  saponin 
comes  out  too  high  by  this  method — notably  the  tincture  from  Span- 
ish leaves  which  I  mentioned  before — although  when  the  drug  is 
taken  by  the  mouth  the  action  is  weak,  digitonin  (saponin)  being 
unabsorbed  in  the  intestine. 
A  sample  containing  a  high  percentage  of  water  soluble  gluco- 
sides  was  under  strength  when  tested  by  this  method,  although  on 
perfusion  its  action  was  quite  powerful  and  desirable. 
The  objections  to  the  Minimum  Lethal  Dose  method  (by  injec- 
tion) are: 
1.  A  large  number  of  frogs  is  required  for  each  sample. 
2.  A  vivisection  license  is  necessary,  and  consequently  the  chem- 
ist cannot  standardize  his  samples  by  this  means. 
Up  to  the  present  the  best  standardization  put  forward  for  digi- 
talis preparations  is  Dr.  Martindale's  colorimetric  estimation. 
This  method  gives  very  concordant  results  with  the  M.L.D. 
values  and  eliminates  frog  variation ;  but,  unfortunately,  it  does  not 
differentiate  between  saponin  and  digitalein,  and,  furthermore,  does 
not  give  the  full  digitoxin  strength,  some  of  the  latter  being  un- 
doubtedly precipitated  along  with  colloidal  matter  on  the  dilution  of 
the  original  tincture  with  water  (the  alcohol  strength  not  being  suf- 
ficient to  hold  it  in  solution)  or  is  "absorbed"  by  the  kieselghur 
used  in  filtration.  As  the  digitoxin  content  does  not  run  parallel 
with  the  digitalein  in  all  samples  (which  I  mentioned  before),  this 
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