AmMJa0y,r^P78arrn'}      Fluid  Extracts  by  Repercolation,  221 
In  interpreting  the  results  of  this  table  the  disturbing  effect  of  the 
trials  of  different  degrees  of  moistening  and  different  length  of  macera- 
tion, must  be  borne  in  mind  as  largely  concerned  in  the  discordant 
results.     But  this  discordance  fairly  shows  first  the  necessity  for  care- 
ful investigations  and  trials,  since  otherwise  the  discords  would  have 
escaped  observation  ;  and  next  shows  the  certainty  with  which  each 
operation  tends  to  control  and  correct  the  results  of  the  preceding  one 
until  uniformity  be  reached.    The  residue  of  each  percolation  was 
critically  examined  by  tasting,  and  in  none  was  the  exhaustion  absolute. 
As  the  percolators  were  emptied  the  upper  eighth  would  be  tasteless  as- 
a  rule  ;  then  the  bitter  taste  would  be  perceptible  and  would  gradually 
increase  to  the  bottom.  At  three-fourths  down  it  would  be  very  decided, 
and  the  remaining  fourth  would  be  pretty  strongly  bitter.  The  different 
percolations  were  only  moderately  uniform  among  themselves,  and  the 
want  of  uniformity  was  mainly  in  the  lower  third  of  the  residue.  But 
the  residues  were  much  more  uniform  among  themselves  than  were  the 
proportion  of  extract  obtained,  and  all  were  fairly  exhausted.    The  first 
and  sixth  percolations  gave  the  most  thoroughly  exhausted  residues, 
and  yet  the  extract  obtained,  as  shown  by  the  table,  was  about  two  to 
one.    This  shows  in  a  striking  way  that  the  extractive  matter  is  not  a 
measure  of  the  exhaustion  as  judged  by  the  bitterness  of  the  residue, 
Therefore  in  using  the  quantity  of  extract  as  a  guide  to  exhaustion,  if 
the  quality  of  the  extract  be  not  ascertained  the  condition  of  the  residue 
must  be  used  as  a  check  upon  the  extract  as  a  guide. 
The  general  result  however,  as  shown  by  even  a  glance  at  the  table, 
— a  result  that  could  be  obtained  in  no  other  way, — though  favorable 
to  repercolation,  is  unexpectedly  unfavorable  to  the  menstruum  used 
because  of  the  overloading  and  masking  effect  of  the  excess  of  soluble 
extractive  matter  in  this  exceptionally  rich,  soft,  soluble  bark.  There- 
fore another  percolation, — the  seventh  of  this  series, — was  made  with 
another  grade  of  Cinchona  using  the  same  weak  percolates  and  men- 
struum. This  Cinchona  was  the  poorest  in  the  writer's  possession.  It 
is  from  the  C.  officinalis  cultivated  in  Ceylon,  and  contains  between  4. 
and  5  per  cent,  of  total  alkaloids,  of  which  about  three-fourths  is 
quinia.  Therefore  though  still  much  richer  than  the  U.  S.  P.  Yellow 
Cinchona  it  is  much  nearer  to  it  than  the  Java  Cinchona  is.  This  8 
ounces  =226*7  grams,  of  the  new  powder  was  as  well  exhausted  as  the 
other  percolations  with  1136*33  grams,  of  percolate  in  5  portions  of 
