134  Examination  of  Vegetable  Products .  {^i^Slim^' 
ents.  Chemical  analysis  determines  the  amount  of  fibre,  starch, 
protein,  oil,  etc. ;  microscopical  analysis  determines  the  shape,  size, 
and  other  characteristics  of  the  cells  and  cell  contents.  Chemical 
analysis  usually  stops  with  the  mere  determination  of  the  amount  of 
chemical  constituents ;  micros copical  analysis  goes  further  and 
names  the  particular  product  from  which  they  were  derived. 
Chemical  analysis  answers  a  question  only  in  scientific  terms ; 
microscopical  analysis,  in  terms  which  all  can  understand. 
In  many  cases,  the  best  idea  of  a  material  is  gained  by  following 
out  both  lines  of  investigation.  By  chemical  analysis  we  learn  the 
percentage  of  protein,  fiber,  starch,  etc.,  but  not  the  ingredients 
from  which  they  were  derived ;  by  microscopical  analysis  we  learn 
the  ingredients,  but  usually  gain  only  an  approximate  idea  of  their 
proportion.  Given  the  results  of  both  analyses,  we  may  often  calcu- 
late with  some  exactness  the  percentage  of  the  different  materials 
present. 
If,  for  example,  we  find  in  a  sample  of  wheat  bran  n  instead 
of  16  per  cent,  of  protein,  and  15  instead  of  8  per  cent,  of  fiber, 
we  know  it  is  not  pure  bran  but  we  do  not  know  the  adulterant ; 
if  we  find  corn-coib  tissues  under  the  micro'Scope,  we  learn  the  adulter- 
ant but  not  the  amount.  Knowing  that  the  material  is  a  mixture 
of  bran  and  ground  corn-cob,  and  knowing  the  average  percentage 
of  protein  and  fiber  in  both,  we  are  in  a  position  to  calculate  from 
the  results  of  the  chemical  analysis  the  relative  amounts  of  these 
ingredients. 
Again,  if  we  find  in  ground  mace  40  per  cent,  instead  of  20  per 
cent,  of  fixed  oil,  we  know  it  is  not  pure  mace;  if  we  find  under 
the  microscope  a  large  amount  of  tissues  of  the  Bombay  mace, 
a  material  worthless  as  a  spice  containing  about  60  per  cent,  of 
fixed  oil,  we  learn  the  adulterant.  Knowing  all  this,  and  knowing 
the  average  percentage  of  oil  in  true  mace  and  Bombay  mace,  we 
have  the  data  for  calculating  roughly  the  percentage  of  each  in 
the  mixture. 
Still  again,  if  in  a  textile  fabric  we  find  a  certain  percentage  of 
organic  fiber  insoluble  in  boiling  alkali,  we  know  that  the  fabric 
is  not  all  wool.  If  under  the  microscope  we  identify  this  insoluble 
fiber  as  cotton,  we  have  found  the  missing  link  in  the  chain  of 
evidence. 
In  the  analysis  of  complicated  mixtures,  we  must  often  rely 
entirely    on   microscopical   examination.    For  example,  chemical 
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