10        ECONOMY  IN  THE  USE  OF  ALCOHOL  IN  PERCOLATION. 
upon  plates  shielded  from  dust,  at  ordinary  temperatures.  The 
mode  of  drying  has  much  to  do  with  the  color  and  lightness  of 
the  powder,  more  even  than  the  quantity  of  water  used  in  the 
precipitation.  The  washing  also  has  much  to  do  with  the  charac- 
ter of  the  powder,  for  if  much  of  the  gummy  extractive  matter 
be  left  in,  it  will  dry  by  contracting  and  will  become  heavy  and 
dense,  difficult  to  rob  up,  and  yield  a  heavy  powder  of  less  thera- 
peutic value,  because  more  difficult  to  incorporate  intimately 
with  corrigents  and  excipients. 
This  resin  is  neither  a  very  active  nor  a  very  prompt  cathartic 
in  any  reasonable  dose,  but  on  the  contrary  is  rather  slow 
though  certain.  It  prominently  affects  the  upper  portion  of  the 
alimentary  canal,  as  aloes  does  the  lower  portion,  and  upon  this 
prominent  characteristic  its  value  as  a  purgative  chiefly  depends. 
To  this  circumstance,  and  perhaps  to  this  alone,  it  owes  its 
reputation  as  a  chologogue,  its  action,  by  continuity  and  contig- 
uity, being  extended  to  the  liver  and  gall  bladder.  Hence  it 
becomes  important  to  give  it  in  such  a  form  as  to  secure,  beyond 
a  doubt,  its  solubility  in  the  stomach.  With  many  persons  its 
operation  is  harsh  and  unpleasant,  and  the  effects  and  results  are 
unsatisfactory ;  bat  in  a  large  majority  of  cases,  when  used  with 
skill  and  judgment,  it  becomes  a  valuable  agent.  Its  therapeutic 
properties  have  as  yet  been  imperfectly  studied,  and  its  uses  are 
undeveloped.  A  careful,  industrious  and  earnest  observer,  is 
however,  now  at  work  with  it,  and  the  paper  of  Dr.  Caleb  Green, 
of  Homer,  N.  Y.,  will  doubtless  add  to  the  present  stock  of 
knowledge  of  this  substance.  It  appears  to  be  best  adapted  to  the 
purposes  of  a  slow  aperient,  or  at  least  such  is  the  character  it 
has  gained  among  practitioners  in  this  neighborhood,  and  when 
properly  guarded  and  corrected,  and  given  in  small  doses  adjus- 
ted to  a  definite  and  well  understood  condition  and  object,  it 
generally  grows  in  favor  with  those  who  jise  it,  so  that  few  physi- 
cians who  learn  its  peculiarities  and  how  to  use  it,  ever  give  it  up. 
The  mode  of  administration  appears  to  be  of  much  import- 
ance. Given  alone  or  unguarded  it  seems  to  shock  the  mucous 
linings,  and  to  produce  nausea  and  griping  of  a  peculiar  kind, 
confined  to  the  upper  portion  of  the  intestines.  But  when 
properly  comminuted  and  shielded,  its  operation  is  generally 
