784 
The  Theory  of  Percolation. 
(  Am.  Jour.  Pharm. 
(    November,  1920. 
The  situation  in  respect  to  menstruum  is  excellent  mainly  be- 
cause they  have  been  chosen  as  a  result  of  many  experiments  the 
conditions  of  which  point  definitely  and  unmistakably  to  the  correct 
choice.  Menstrua  are  usually  chosen  much  in  advance  of  any  very 
detailed  analysis  of  the  drug  plant  and  knowledge  of  the  chemical 
and  physical  nature  of  the  active  constituents.  Indeed,  our  lack 
of  knowledge  in  this  respect  has  been  responsible  for  much  empiricism 
in  the  application  of  menstrua.  We  have,  however,  succeeded  in 
establishing  a  proper  solvent  for  every  important  drug,  though  in 
most  cases  our  products  are  not  free  from  precipitation. 
We  are  indebted  to  Procter^  for  initiating  and  prosecuting  much  of 
the  work  which  has  been  done.  Lloyd, ^  Savery,^  Remington,*  and  a 
host  of  others  have  supplemented  this  work.  Remington^  and  Squibb^ 
have  advocated  the  use  of  acetic  acid  menstrua,  proposing  to  elimi- 
nate alcohol  altogether  in  extracting  certain  drugs.  WuUing^  and 
Feil^^  supported  the  idea  but  Thompson^  and  Dohme^*  opposed  it. 
As  a  result  of  thsi  work  acetic  acid  menstrua  were  directed  by  the 
1900  pharmacopoeia.  The  preparations,  however,  failed  to  meet  with 
the  approval  of  physicians  and  were  dropped  in  the  last  revision 
(1910). 
The  use  of  glycerin  in  menstrua  as  a  preservative  agent  was  early 
suggested  by  Taylor^  and  proved  a  distinct  advance  in  fiuidextract 
technique.  Lloyd^  recommends  it  for  drugs  which  contain  tannins 
and  Lehman regarded  it  valuable  for  drugs  whose  active  principles 
are  soluble  in  both  alcohol  and  water  but  discards  it  for  mucilaginous 
and  resinous  drugs.    Moore opposed  the  use  of  glycerin  in  menstrua 
I  This  Journal,  Vol.  19,  182,  (1847);  23,  218,  (1851);  24,  207,  (1852);  26,  28, 
(1854);  25,  410,  (1853);  28,  22,  (1856);  31,  530,  (1859). 
-  Pharm.  Rund.  1889,  165.  : 
3  This  Journal,  Vol.  23,   119,   (185 1). 
4  This  Journal,  Vol.  46,  7,  (1874).    Cf.  Squibb,  This  Journal,  Vol.  39,  289; 
398;  513,  (1867). 
5  This  Journal,  Vol.  69,  121,  (1897);  70,  543,  (1898). 
^  This  Journal,  Vol.  71,  i,  (1899);  72,  i,  (1900). 
^  Pharm.  Era,  1898,  796. 
8  Proc.  A.  Ph.  A.  1908,  883. 
9  This  Journal,  Vol.  71,  67,  (1899). 
Proc.  A.  Ph.  A.  1904,  337. 
II  This  Journal,  Vol.  37,  50,  (1865). 
12  Proc.  A.  Ph.  A.  1877,  408. 
^3  This  Journal,  Vol.  49,  346,  (1877). 
This  Journal.  Vol.  46,  551,  (1874). 
