IOO 
Correspondence. 
r  Am.  Jour.  Pharru 
\    February,  1897, 
should  and  will  contain  all  the  desired  active  principles  of  the  drug. 
If  this  is  true,  it  follows  logically  and  necessarily  that  if  such  a 
fluid  extract  be  diluted  by  the  proper  menstruum  to  the  strength  of 
the  corresponding  tincture,  the  resulting  dilution  will  be  equal  in 
therapeutic  effect  to  the  latter.  But  one  reservation  must  be  made 
here.  The  equality  will  be  disturbed,  if  the  liquid  added  as  diluent 
to  the  fluid  extract  causes  such  a  disturbance  of  the  dissolved  mat- 
ters that  some  of  the  latter,  either  at  once  or  gradually,  lose  their 
solubility  and  become  precipitated.  That  there  are  drugs  behaving 
in  such  a  manner  cannot  be  denied,  and  it  must,  at  the  same  time,  be 
stated  that,  while  the  matters  first  thrown  out  of  solution  are  proba- 
bly, in  themselves,  always  inert,  yet  they  are  apt  to  carry  along  with 
them  some  of  the  useful,  active  constituents,  thereby  causing  the 
tincture  made  by  dilution  from  the  fluid  extract  to  become  weaker 
in  therapeutic  strength  than  that  made  originally  as  a  tincture  from 
the  drug  direct.  Moreover,  it  is  well  known  that  when  such  pre- 
cipitation once  begins,  it  is  liable  to  progress  for  a  long  time,  so  that 
even  filtration  will  not  interrupt  the  process  of  deterioration.  A 
notable  example  of  this  class  of  drugs  is  cinchona  bark,  particu- 
larly the  red  variety. 
If  the  statements  thus  far  made  are  agreed  to,  it  seems  to  me 
that  we  may  formulate  a  few  propositions  regarding  the  subject, 
which  will  probably  also  be  accepted,  though  there  is  likely  to  arise 
a  difference  of  opinion  as  to  whether  it  is  practicable  at  all,  or  at 
least  as  to  how  far  it  is  practicable  to  apply  the  propositions.  It 
should  be  understood  that  in  comparing  any  fluid  extract  and  tinc- 
ture made  from  one  and  the  same  drug,  they  are  assumed  to  have 
been  prepared  from  known  quantities  of  the  drug  of  known  strength, 
and,  therefore,  to  be  commensurate.  The  propositions  which  I  wish 
to  make  are  as  follows  : 
(1)  If  a  fluid  extract  differs  from  a  tincture  only  in  the  quantity 
of  the  solvent  or  menstruum,  and  if  the  dilution  of  the  former  to 
the  strength  of  the  tincture  by  the  addition  of  more  of  the  solvent 
throws  nothing  out  of  solution,  the  two  tinctures  must  be  alike  in 
the  quantity  of  active  constituents,  and,  therefore,  be  alike  in  thera- 
peutic effect. 
(2)  If  the  dilution  of  a  fluid  extract  to  the  strength  of  the  corre- 
sponding tincture  by  the  addition  of  even  the  most  favorable  men- 
struum causes  a  precipitation,  the  two  tinctures  may  still  be  re- 
