212  Keeping  Properties  of  Digitalis.  {Am'£^'^am- 
found  a  unit  of  81.5  mg.  of  leaf  per  kilo.  (Three  tests,  84.6,  71.0 
and  89.0  mg.  per  kilo  respectively).  On  the  same  day  we  tested 
the  tincture  from  which  the  dilution  had  been  made  and  found  it 
to  have  a  cat  unit  of  62.2  mg.  of  leaf  per  kilo  (two  tests,  61.8  and 
62.7  mg.  respectively).  In  a  period  of  seventeen  days,  then,  this 
aqueous  dilution  of  a  tincture  of  digitalis  had  lost  31  per  cent,  of  its 
original  activity.  It  is  remarkable  that  it  had  not  lost  more  than 
this,  and  the  low  temperature  of  the  room  may  be  partly  responsible 
for  its  comparatively  moderate  deterioration. 
The  deterioration  of  aqueous  preparations  of  digitalis  has  long 
been  recognized  and  this  fact  has  recently  been  recalled  by  Cushny," 
who  says  of  strophanthus,  squill  and  digitalis  that  "  Their  active 
principles  readily  undergo  decomposition  when  the  tincture  is 
diluted  with  water.    .  . 
We  are  disposed  to  remark  that  it  is  irrational  to  dispense  the 
tincture  of  digitalis  already  diluted  with  water,  or  with  an  aqueous 
vehicle.  The  physician  should  order  the  necessary  dilution  to  be 
made  by  the  patient  each  time  that  he  takes  the  prescribed  dose, 
or  should  employ  a  vehicle  containing  a  sufficient  amount  of 
alcohol. 
There  is  one  other  preparation  which  deserves  notice,  only  to  be 
condemned.  This  is  the  acetic  fluid  extract.  A  sample  of  this 
preparation  which  was  made  in  1901  was  found  to  be  practically 
without  digitalis  action.  In  order  to  avoid  the  disturbing  influence 
of  the  acetic  acid  present  in  the  specimen  5.0  c.c.  were  neutralized 
with  an  excess  of  sodium  bicarbonate  and  evaporated  on  the  water 
bath  to  a  soft  extract.  This  was  treated  several  times,  while  still 
on  the  water  bath,  with  strong  alcohol ;  the  alcoholic  extract  was 
decanted  and  evaporated.  It  was  then  taken  up  with  5.0  c.c.  of 
diluted  alcohol,  making  a  clear  solution.  This  was  further  diluted 
with  normal  salt  solution  to  make  50.0  c.c.  This  solution  was  then 
tested  on  a  cat  in  the  usual  way.  At  the  end  of  an  hour  the  animal 
had  received  a  quantity  which  represented  1000  mg,  of  digitalis 
leaf  per  kilo.  As  the  animal  showed  no  perceptible  effect  save 
slight  slowing  of  the  heart  (due,  in  all  probability  to  the  fluid  in- 
jected), it  was  released.  Five  hours  later  it  had  still  shown  no 
positive  digitalis  effect. 
This  same  preparation — acetic  fluid  extract — was  injected  into 
11  Brit.  Med.  Jour.,  1912,  II,  p.  685. 
