Am'Ma°yri9Pi3arm'}       Keeping  Properties  of  Digitalis.  211 
This  specimen  of  fluid  extract  of  digitalis  had,  therefore,  prob- 
ably undergone  no  deterioration  in  thirty  years,  since,  as  stated,  it 
was  far  more  active  than  the  average  fluid  extract  of  digitalis  now 
in  use. 
England  3  contends  that  heat,  even  when  moderate  and  applied 
for  a  comparatively  short  time,  causes  enormous  loss  of  activity  in 
the  fluid  preparations  of  digitalis.  Foeke  controverts  this  state- 
ment by  the  results  of  his  experience  in  the  concentration  by  heat 
on  the  water  bath  of  aqueous  infusions  of  digitalis  when  they  are 
too  weak  to  be  tested  on  the  frog.  He  recommends  concentration 
by  50  per  cent,  and  finds  that  the  process  causes  no  reduction  in 
activity.  In  this  country  nearly  all  of  those  who  use  the  frog 
method  of  standardizing  digitalis  preparations  employ  heat  to  re- 
duce the  amount  of  the  alcohol  before  testing  such  preparations  as 
the  tincture. 
To  these  statements  with  regard  to  the  influence  of  heat  we 
may  add  that  we  found  a  sample  of  solid  extract  of  digitalis,  which 
was  made  in  1908,  and  which  was  said  to  represent  two  and  one- 
half  times  the  weight  of  leaf,  to  have  a  cat  unit  of  52  mg.  per 
kilo  (that  is,  128  mg.  of  the  leaf).  There  was  no  obvious  loss 
in  activity,  although  the  preparation  had  been  reduced  to  the  con- 
sistency of  a  solid  extract  by  means  of  evaporation  in  the  presence 
of  heat. 
At  this  point  we  decided  to  stop  further  testing  of  the  dried 
leaf  and  of  those  pharmacopceial  preparations  of  digitalis  made  with 
a  menstruum  containing  50  per  cent,  or  more  of  alcohol,  for  it  was 
evident  that  deterioration  does  not  occur  to  any  considerable  degree 
in  such  forms  of  the  drug,  under  ordinary  conditions. 
It  is  unnecessary  to  mention  the  infusion  further  than  to  state 
that  frequent  observations  confirm  the  well  known  fact  that  it  is 
prone  to  undergo  rapid  deterioration  even  in  the  presence  of  a  small 
amount  of  alcohol,  such  as  is  now  used. 
Deterioration  of  digitalis  in  the  presence  of  water  is  further  well 
illustrated  by  the  following  experience:  We  diluted  a  tincture  of 
digitalis  of  known  strength  with  nine  parts  of  normal  saline  solu- 
tion and  set  it  aside,  closely  stoppered,  for  seventeen  days.  It  was 
exposed  to  the  light  during  this  time,  and  for  the  most  part  was  in 
an  unheated  room,  though  on  some  days  it  was  exposed  to  a  tem- 
perature of  700  F.  for  as  much  as  five  hours  at  a  time.  On  the 
seventeenth  day  after  dilution  we  tested  this  solution  on  cats  and 
