470 
rochleder's  proximate  analysis. 
some  bodies  to  disappear,  which  prevent  such  observations.  In  chemical 
relations  merely,  nothing  results  from  these  observations,  as  bodies  are 
present  which  behave  towards  certain  reagents  precisely  as  many  hundred 
other  bodies,  some  of  which  we  know  accurately,  others  very  little  or  not 
at  all.  Of  bodies  which  are  colored  brown  by  iodine,  and  such  as  are  col- 
ored red  by  sulphuric  acid  with  the  addition  of  sugar,  there  is  an  innu- 
merable quantity.  From  such  reactions  on  certain  bodies,  to  establish 
certain  classes  of  bodies,  is  folly. 
To  give  a  method  for  the  microsopic  examination  of  vegetable  substances 
whose  composition  has  been  previously  ascertained  with  exactness,  and 
whose  constituents  have  been  accurately  investigated  with  regard  to  their 
behaviour  to  the  various  reagents,  is  at  the  present  time  an  impossibility. 
We  have  a  mass  of  difficulties  therein  to  overcome,  and  the  result  of  an 
investigation  is  frequently  a  doubtful  when  even  a  probable  one,  as  we  may 
have  often  and  cautiously  made  observations,  at  least  with  regard  to  one 
or  more  constituents,  when  there  was  also  frequently  no  difficulty  in  pro- 
curing certainty  concerning  other  constituents. 
§  8.—  Conclusion. 
So  far  as  was  practicable  in  the  present  position  of  our  knowledge,  I  be- 
lieve that  I  have  supplied  a  method  for  the  examination  of  plants  or  their 
parts  which  does  not  easily  permit  a  body  to  be  overlooked  which  exists 
therein  as  a  constituent.  I  believe,  also,  that  by  following  the  method 
given  with  some  attention,  suitable  methods  of  separation  can  be  easily  de- 
vised to  procure  as  many  of  the  individual  constituents  as  are  necessary 
for  the  performance  of  a  more  minute  examination  of  them,  which  will  af- 
ford us  again  useful  hints  for  devising  improved  methods  of  separation. 
"When  a  minute  examination  of  a  constituent  is  intended,  and  consequent- 
ly a  sufficient  quantity  is  to  be  prepared  for  this  purpose,  it  is  an  unneces- 
sary labor  and  a  useless  loss  of  time,  when  the  order  of  analysis  here  de- 
scribed is  pursued,  to  separate  and  prepare  all  the  bodies  which  are  contem- 
poraneously present.  We  often  attain  this  object  very  quickly  when  a  cer- 
tain quantity  of  the  material  is  employed  for  the  preparation  of  a  constit- 
uent, and  in  this  undertaking  we  have  only  a  regard  to  this  one  constitu- 
ent, and  are  disposed  to  sacrifice  the  remaining  ones.  This  shorter  and 
simpler  method  for  the  preparation  of  individual  constituents  can  only  be 
devised  from  the  experiences  which  we  have  made  by  a  systematic  analy- 
sis, which  has  enabled  us  to  learn  all  the  constituents  present,  and  given 
us  the  means  to  prepare  smaller  quantities  of  the  individual  constituent 
for  the  examination  of  its  behaviour  with  other  bodies,  as  far  as  it  is  ne- 
cessary, to  discover  methods  of  preparation  based  on  these  experiences, 
which  will  enable  us  to  procure  larger  quantities  of  the  constituent  for 
further  investigation  in  the  shortest  possible  time  and  with  the  least  ex- 
pense.   When  we  have  prepared  sufficient  quantities  of  all  the  constituents 
