8'6 
HOCHLEDER'S  proximate  APTAr.YSrS- 
Section  1. — Mechanical  ireatment  of  the  material   preliminary  to  its 
investigation . 
When  we  desire  to  be  able  to  learn  the  composition  of  a  vegetable  sub- 
stancje,  the  first  requisite  is  to  simplify  and  facilitate  the  subsequent  chemi- 
cal operations  by  a  suitable  mechanical  preparation  of  the  substance  to  be 
examined. 
If  we  were  in  a  position  so  to  dismember  a  plant  that  orAj  its  equally 
similiir  ceils  were  separated  and  subjected  to  a  chemical  ia>estigation,  not 
.jiQty  would  the  analysis  be  thereby  greatly  simplified,  beta  source  of  error 
would  be  quite  removed — the  formation  of  bodies  notoriginally  present,by  the 
action  of  the  constituents  of  dissimilar  cells  on  one  ariother.  But  such  an 
aaatomical  preparation  of  the  material  for  the  subsequent  chemical  investiga- 
tlo'ii  is  an  impossibility.  Now,  as  the  separation  of  the  individual  tissues  of  a 
plant,  at  least  of  such  a  large  quantity  of  the  material  as  we  require  for  a 
chemical  investigation,  belongs  to  the  limits  of  the  impossible,  we  must 
accomplish  at  least  the  possible  in  this  respect  by  the  mechanical  separation 
of  the  parts  as  completely  as  practicable.  How  far  this  can  be  eftected  in 
cortaio  cases  depends  on  the  structure  and  anatomical  relations  of  the  sub- 
staace  to  be  examined. 
To  render  the  substance  intended  for  examination  suitable  for  treatment 
with  liquids,  it  must  be  comminuted.  The  more  paints  of  contact  pre- 
s-juted  by  the  material  to  the  liquid,  the  better  it  is..  The  comminution 
Citinot  easily  be  carried  too  far  with  materials  which  cannot  be  penetrated 
with  the  liquid  which  is  intended  for  their  extraction,  In  this  case  merely 
moistening  of  the  surface  of  the  smallest  portions  takes  place.  The  smaller 
these  portions,  the  greater  the  surface,  the  more  compietelj  the  extraction 
with  the  solvent  is  accomplished.  With  a  material  which  is  readily  pene- 
trated with  the  solvent  employed,  a  careful  comminution  is  superfluous.  In 
so  far  as  a  substance  swells  up  by  means  of  the  fluid  used  for.its  extraction, 
it3  minute  division  is  objectionable.  Under  such  circumstances  a  gela- 
tiaous  mass  results,  which  absorbs  and  retains  much  fluid,  the  solvent  can- 
not be  separated,  and  when  pressure  is  employed  for  this  purpose,  the 
pasty  mass  escapes  through  all  the  pores  of  the  press-elotSi. 
Frequently  a  very  fine  powder  of  the  substance  cannot  be  prepared  on 
account  of  the  peculiar  tenacious  property  of  the  materirJ.  Nevertheless, 
if  it  be  desirable  to  divide  such  a  substance  as  much  as  possible,  it  may  be 
often  readily  effected  after  the  removal  of  the  greatest  part  of  several  con- 
^atituents. 
Often  a  certain  degree  of  moisture,  the  presence  of  water,  renders  the 
smbstance  tenacious  and  elastic,  so  that  it  is  difficult  to  pulverise  it.  A 
o;irefal  drying  suffices  in  such  cases  to  deprive  the  material  of  its  tenacity, 
and  to  render  it  pulverizable.  For  example,  it  is  extremely  difficult  to  beat 
t'J  a  fine  powder  coffee  beans  in  the  condition  in  which  they  exist  in  com- 
merce.   However,  this  is  easily  effected  when  they  are  exposed  for  several 
