USE  OF  FUNNELS  IN  DISPLACEMENT. 
329 
Drugs  which  swell  very  much  when  moistened,  give  the  most 
trouble  in  percolation  in  the  ordinary  straight  cylinders  used, 
the  reason  is  undoubtedly  to  be  found  in  the  compression  oc- 
casioned by  the  swelling  of  the  mass  of  vegetable  matter  in  the 
cylinder.  If  tightly  packed  when  introduced,  this  expansion 
must  cause  an  excessive  compression  of  the  particles  upon  each 
other  and  a  consequent  closing  up  of  the  pores  through  which 
the  menstruum  is  designed  to  percolate. 
This  compression  often  amounts  to  a  complete  plugging 
up  of  the  apparatus,  even  when  the  powder  has  been  previously 
macerated,  and  has  not  been  tightly  packed;  but  when  it  has  been 
only  dampened,  not  swelled,  before  packing,  as  directed  by 
Grahame,  it  becomes  so  completely  compacted  together  as  it 
swells,  as  entirely  to  prevent  percolation. 
This  difficulty,  which  every  tyro  must  be  familiar  with,  is  com- 
pletely obviated  by  the  use  of  a  common  funnel,  with  a  loose 
plug  of  cotton  in  the  tube  ;  the  pressure  occasioned  by  the  ex- 
pansion of  the  mass  as  it  becomes  saturated  with  the  liquid,  in- 
stead of  being  confined,  tends  upwards  as  well  as  outwards,  and 
thus  as  the  mass  becomes  tighter  it  relieves  itself  by  rising  in 
the  funnel,  and  is  prevented  from  becoming  so  compressed  as 
to  interfere  with  its  capillarity. 
With  the  use  of  the  common  funnel,  large  or  small  at  pleas- 
ure, I  find  my  experience  to  coincide  completely  with  that  of 
Prof.  Grahame.  One  experiment  may  be  mentioned  as  illus- 
trating the  success  of  the  process  ;  10,000  grains  of  English 
Colchicum  corm,  was  powdered  by  Swift's  Drug  Mill,  to  about 
the  fineness  indicated  by  Grahame,  dampened  with  diluted  Acetic 
Acid,  and  packed  with  a  pestle,  as  tightly  as  possible  in  a  large 
glass  funnel  ;  a  little  more  than  a  quart  of  the  same  menstruum 
was  then  added  and  thirty  fluid  ounces  of  liquid  was  obtained, — this 
first  portion  on  evaporation,  yielded  1750  grains  of  extract,— a 
second  portion  of  menstruum  was  now  added,  and  another  thirty 
tfluid  ounces  passed, — this  yielded  390  grains,  and  a  third  por 
ion  of  the  same  bulk  yielded  only  38  grains. 
The  aggregate,  2178  grains,  (not  quite  22  per  cent.)  is  rather 
less  than  I  have  obtained  from  some  previous  operations,  but 
allowance  must  be  made  for  the  quality  of  the  drug,  which,  in 
this  instance,  though  remarkably  fine,  contained  the  outer 
