727 
Standard  Tincture. 
Tincture  213. iS. 
Therapeutic  value  (A)  , . .  | 
(W.  S.  Glucosides)   j 
Total  Glucosides  j 
Value  B  j 
Toxic  Value  (B-A)  
1 
Ratio 
B-A 
A 
=  1.66 
thus  showing  that  the  Tincture  (213.18)  is  relatively  more  toxic  and 
therefore  no:  so  benericial  as  the  Standard  Tincture. 
A  desirable  standardization  of  any  tincture  would  be  as  follows : 
( 1  Conduct  two  colorimetric  estimations  by  process  A  and  B.  Note 
the  M.L.D.  value,  and  the  therapeutic  value  (A).    Then  check  the 
M.L.D.  value  from  experiment  B,  and  work  out  the  ratio  — 
An  increased  M.L.D.  value  from  (B)  denotes  excess  toxicity,  which 
would  be  confirmed  by  the  ratio- — — — .    The  excess  toxicity  may 
be  due  to  either  saponin  or  digitoxin  (although  for  oral  medication 
the  presence  of  saponin  is  of  little  import,  as  I  mentioned  earlier). 
(2)  Carry  out  the  perfusion  experiment,  using  male  frogs  and 
the  tincture  1  per  cent,  in  Ringer's  solution,  continuing  the  perfusion 
until  the  heart  stops.  Then  calculate  the  number  of  drops  required 
for  100  Gm.  frog,  and  find  the  result  on  the  M.L.D.  graph.  Notice 
the  time  taken  to  kill  the  heart,  as  this  gives  some  guide  as  to  the 
relative  quantities  of  the  several  glucosides  present — e.g.,  a  long  trac- 
ing with.  say.  0.5  to  0.6  M.L.D.  would  indicate  a  high  water  soluble 
glucosidal  value  and  a  corresponding  low  digitoxin  value  and  vice 
versa.  The  tracing  would  also  show  the  therapeutic  action;  any  ab- 
normal variation  in  the  composition  of  the  tincture  being  easily 
detected.  (This  was  explained  at  length  in  the  treatise  which  I 
summarized  previously.) 
A  second  "two  or  three  minutes"  perfusion  on  another  frog, 
reperf using  Ringer's  solution  again  to  recovery,  would  give  us  useful 
information  as  regards  therapeutic  activity.  The  M.L.D.  values 
obtained  from  the  graph  could  be  checked  by  injection  if  desired  by 
using  four  frogs  only,  the  doses  given  being 
(1)  Slightly  below  the  calculated  M.L.D. 
(2)  and  (3)  M.L.D.  as  calculated. 
(4)  Slightly  above  the  calculated  M.L.D. 
