Am.  Jour.  Pharm. ) 
November,  1920.  ) 
The  Theory  of  Percolation. 
783 
voluminous,  but  much  remains  to  be  done  before  its  role  in  percolation 
is  made  clear. 
We  cannot,  therefore,  conclude  in  favor  of  any  one  general 
optimum  fineness  for  a  drug.  We  may  say  that,  the  stronger  the 
menstruum  to  be  used  is  in  alcohol  the  finer  the  drug  may  be  powdered 
and  as  strongly  alcoholic  menstrua  tend  to  shrink,  instead  of  swelling, 
vegetable  fibres  and  cells,  the  finer  the  drug  the  better  in  such  cases. 
In  general,  the  drug  should  be  ground  to  as  fine  a  powder  as  will  be 
permitted  by  its  character,  the  menstruum,  the  quantity  being  ex- 
tracted, and  the  time  available. 
PROF.  WILLIAM  PROCTER,  JR. 
A  pioneer  advocate  of  the  pharmaceutical  application  of  percolation. 
When  the  drug  has  been  ground  to  the  desirable  fineness  the  next 
step  in  the  process  is  the  moistening  of  it  and  this  brings  up  the  selec- 
tion of  the  menstruum.  Here  we  find  that  a  multitude  of  pharmacists 
have  done  very  good  and  careful  work  for  it  was  early  recognized 
that  not  only  the  proper  extraction  but  the  permanence  of  the  pro- 
duct depends  upon  the  suitability  of  the  menstruum.  In  choosing 
a  menstruum  the  principles  enunciated  in  the  discussion  of  the  classi- 
fication of  drugs  must  be  borne  in  mind  as  well  as  the  idea  of  the 
ideal  menstruum  which  is  such  a  one  that  will  perfectly  dissolve  the 
active  constituents  and  exclude  undesirable  ingredients  furnishing  a 
product  that  may  be  readily  preserved. 
