396  Stability  of  Digitalis  Leaf  Extracts.    { ju^e.^^S^b.^^^"""' 
paper,  but  their  findings  are  certainly  entirely  different  from  those 
obtained  by  the  one-hour  frog  method. 
Concerning  the  comparative  activity  of  infusions  and  tinctures 
we  obtain  results  similar  to  the  previous  findings  of  Focke.^  This 
investigator  reports  that  infusions  filtered  through  linen  or  cotton 
give  slightly  higher  results  than  when  filter  paper  is  used.  The 
activity  corresponds  to  about  85  per  cent,  of  that  obtained  in  tinc- 
tures of  equal  concentration.  We  believe  that  this  figure  will  repre- 
sent the  average  finding  when  a  considerable  number  of  samples  are 
investigated  in  this  connection.  Some  of  our  fresher  samples 
yielded  almost  as  much  of  their  activity  to  water  as  to  the  tincture, 
while  in  the  case  of  a  very  old  drug  only  70  per  cent,  of  the  total 
activity  was  found  in  the  infusion.  For  practical  purposes  Focke's 
figure  is  acceptable  and  the  dosage  of  the  infusion  should  perhaps 
be  slightly  higher  (10/9)  than  for  the  powdered  drug.  In  other 
words,  considering  0.06  Gm.  of  digitalis  (4.0  Cc.  infusion)  as  a 
standard  dose  of  the  powdered  leaf,  the  activity  of  the  infusion  will 
require  about  4.4  Cc.  to  yield  the  same  result. 
If  one  bears  in  mind  the  instability  of  aqueous  digitalis  solutions, 
while  reviewing  some  of  the  chemical  studies  of  the  leaf,  it  becomes 
easy  to  comprehend  the  difficulty  of  the  investigators  in  arriving 
at  concordant  results.  Practically  all  the  workers,  including 
Schmiedeberg,  Kiliani  and  Kraft,  have  worked  in  aqueous  media, 
and  we  daresay  that,  dependent  upon  conditions,  various  products 
have  been  isolated  which  represent  various  degrees  of  alteration. 
In  connection  with  the  chemical  investigation  of  the  leaf  it 
appears  to  be  important  to  bear  in  mind  the  fact  that  the  total 
activity  of  the  crude  galenical  extracts  may  greatly  exceed  the  sum 
of  the  isolated  fractions,  even  if  no  chemical  changes  such  as  hydrol- 
ysis were  involved.  This  subject  is  discussed  by  Tschirch  and 
Wolter,^  who  reported  the  interesting  observation  that  the  activity 
of  the  acetone  extract  of  a  salt  saturated  aqueous  solution  of  digi- 
talis represented  but  a  part  of  the  total  activity,  whereas  the  ex- 
tracted fluid  proved  to  be  inactive.  Acetone  extracts  the  active 
principles  from  the  leaf  completely.  They  state  that  this  difference 
in  results  is  to  be  understood  either  by  reason  of  chemical  change  in 
the  active  principles  or  because  in  the  activity  of  crude  extracts 
other  substances  which,  while  they  are  not  in  themselves  active, 
^  Arch.  Pharm.,  249:  323,  191 1. 
2  Schweiz.  Apoth.  Zeit.,  56:  469.    This  Journai,,  91:  471. 
