j^e^igio^^^""^'}    Stability  of  Digitalis  Leaf  Extracts.  397 
have  nevertheless  an  influence  upon  the  active  material.  This 
influence  is  either  in  relation  to  solubility  or  absorption  which  is 
influenced  favorably.  Tschirch  argues  that  the  activity  of  digitalis 
is  an  ensemble  effect  and  is  not  due  to  simply  the  sum  of  individual 
glucosides ;  instead  the  activity  of  each  individual  is  always  influenced 
and  increased  by  the  simultaneous  presence  of  others.  With  the 
successful  isolation  of  individual  glucosides  the  ensemble  activity 
does  not  appear  upon  physiological  testing. 
These  investigators  performed  a  simple  experiment  of  interest 
in  this  connection  and  bring  out  a  point  which  is  overlooked  in  our 
first  paper.  Putting  the  drug  through  Keller's  assay,  they  isolated 
18.5  per  cent,  of  the  activity  in  the  chloroform  shake  out.  The 
exhausted  aqueous  layer  retained  only  26  per  cent,  of  the  activity, 
so  that  by  simple  exhaustion  of  the  aqueous  solution  with  this  inert 
solvent  over  half  the  activity  disappears.  Loss  of  activity  may  be 
due  therefore  not  only  to  spontaneous  changes,  which  are  described 
in  the  experimental  part,  but  also  to  the  destruction  of  loose  native 
combinations  and  the  loss  of  the  mutual  effects  found  only  in  the 
native  drug. 
KXPKRIMENTAI,. 
A.  Some  Observations  upon  the  Comparative  Activity  of  Fresh  Tinc- 
tures and  Fresh  Infusions  of  Digitalis  Made  from  the  Same  Drug. — 
Drug  (F2190)  stocked  November  20,  1918.  A  10  per  cent,  tincture 
assayed  130  per  cent.  (11-30-18). 
10%  Tincture  A'.      10%  Infusion  (A).  A/A'. 
Date.  %  % 
II-30-18   .   130  ...  .... 
1-14-19   135  (F.  E.)  ...   
4-  1-19   130  1 .0 
10-  1-19  no  ...  .... 
9-16-19   105  0.95 
1-15-20   90  .... 
From  these  assays  it  appears  that  in  extracting  this  drug  during 
one  year  the  infusions  and  tinctures  were  almost  equal  (within  the 
limits  of  error  of  the  method). 
Another  drug  was  examined  on  this  point  (G3316) : 
10%  Tincture  (A').  10%  Infusion  (A).  A/A'. 
Date.                                               %  % 
I-I0-20                                                      150  ...  .... 
4-14-20   120  .... 
4-19-20                                      140  .  .  .  o  .86 
