Am'MaTi8P78arm  }     Fluid  Extracts  by  Reper eolation.  215 
shown  that  great  variation  was  produced  by  both  these  elements.  It 
was  at  first  believed  that  4  parts  of  liquid  was  sufficient  to  moisten  8 
parts  of  powder,  and  that  24  hours  was  long  enough  to  macerate,  and 
the  first  two  percolations  of  the  following  series  were  made  with  these 
conditions.  In  the  third  percolation  the  liquid  was  increased  to  5J 
parts,  and  the  maceration  kept  at  24  hours.  In  the  fourth  the  liquid 
was  increased  to  6  parts.  In  the  fifth  it  was  kept  at  6  parts,  and  the 
time  of  maceration  was  extended  to  48  hours.  In  the  sixth  percolation 
it  was  increased  to  7  parts,  and  the  moistened  powder,  covered  closely 
was  allowed  to  stand  8  hours  to  absorb  the  liquid  more  thoroughly. 
Then  the  powder  was  passed  through  a  No.  8  sieve,  packed  pretty 
firmly,  filled  with  weak  percolate  and  then  macerated  for  48  hours, 
making  a  total  maceration  of  56  hours. 
The  first  percolation  of  the  series,  made  with  fresh  menstruum 
throughout,  is  of  course  a  simple  percolation,  and  was  carried  to  prac- 
tical exhaustion.  And  this  practical  exhaustion  was  doubtless  to  within 
5  or  10  per  cent,  of  absolute  exhaustion  of  all  matters  soluble  in  the 
menstruum.  The  residue  was  quite  tasteless  for  more  than  half  way 
down  the  percolator,  and  then  began  to  be  very  slightly  bitter.  This 
bitterness  increased  until  at  the  bottom  of  the  percolator  it  was  quite 
distinctly  bitter,  after  percolation  under  very  favorable  circumstances 
with  nearly  four  times  its  weight  of  menstruum. 
It  is  quite  certain  that  the  extract  obtained  from  a  drug  by 
percolation  is  not  uniform  throughout  the  percolation  in  its  medicinal 
value.  If  the  menstruum  be  well  adjusted  as  a  solvent  of  the  active 
principles  of  the  drug  it  will  dissolve  and  carry  out  the  most  soluble 
portions  first  and  in  largest  proportion,  so  that  although  doubtless  some 
of  the  useful  part  continues  to  be  present  in  all  parts  of  the  percolate 
and  its  extract,  yet  the  proportion  must  diminish  much  more  rapidly 
than  the  proportion  of  extract.  This  point  is  well  shown,  so  far  as 
Cinchona  is  concerned  in  a  table  given  by  the  writer  in  the  "Arner. 
Journ.  of  Pharmacy  "  for  1867  p.  402,  where  each  portion  of  percolate 
and  its  extract  were  assayed  for  the  total  alkaloids  they  contained. 
Hence,  though  the  quantity  cf  dry  extract  yielded  by  different  portions 
of  the  percolate  be  not  a  measure  of  the  medicinal  value  of  the  perco- 
late it  is  still  the  best  guide  that  is  easily  accessible.  Bearing  in  mind 
then,  that  medicinal  exhaustion  by  percolation  is  more  rapid  than  abso- 
lute exhaustion,  and  that  the  dry  extract  which  measures  absolute 
