Amjine>r"i876arm'}  Powdered  Drugs  under  the  Microscope.  245 
Having  given  the  general  characters  of  the  starch  powders,  we  will 
now  pass  on  to  the  consideration  of  the  species  of  interest  to  the 
pharmacist. 
I.   POTATO-STARCH  (Fig.  i). 
This  starch  is  not  officinal,  but  the  ease  of  obtaining  it  and  the  size 
of  the  grains  make  it  the  best  and  most  convenient  form  for  the 
inexperienced  microscopist  to  begin  with.  Besides,  it  is  frequently 
used  and  still  more  frequently  named  as  an  adulterant  of  other  powders 
and  is,  consequently,  important  to  the  pharmacist.  For  examination 
fresh,  it  can  be  easily  obtained  from  the  potato,  nearly  the  whole  of  the 
interior  of  which  is  made  up  of  it. 
It  forms  a  fine,  white,  glistening  powder,  with  small,  irregular, 
pulverulent  masses  intermixed.  It  crackles  slightly  when  rubbed 
between  the  fingers.  When  examined  carefully,  it  can  be  seen  to  have 
a  yellowish  cast  of  color.  It  has  a  slight  taste  like  raw  potato,  and  a 
faint  acrid  odor.  The  latter  is  brought  out  more  decidedly  by  the 
application  of  alcohol  or  chlorhydric  acid. 
The  grains  vary  much  in  size,  due,  probably,  to  unequal  develop- 
ment, the  youngest  being  smallest,  the  greatest  length  attained  is  about 
50//.1  The  form  is  usually  oval,  egg-shaped,  elliptical  or  round-trian- 
gular.   The  smallest  and  youngest  grains  are  nearly  spherical.  The 
detail,  the  following  references  may  prove  useful  :  HassalPs  Adulteration  in  Food 
and  Medicine,  Soubeiran,  Dictionnaire  des  Falsifications;  Wiesner,  Rohstoffe  des 
Pfianzenreiches,  pp.  239-289  5  Planchon,  Determination  des  drogues  simples,  Vol.  II, 
chap.  XIII  ;  Harrington,  American  Naturalist,  April  and  June,  1875,  v°l-  PP- 
193-198,  339-346. 
For  the  examination  of  starch,  Thomas  Greenish  recommends  especially  the 
following  : 
"  Saturate  distilled  water  with  creosote,  and  take  of 
the  filtered  solution,  %v 
Spirit  of  wine,     .....  giss 
Glycerin,       .  .  .  .  .  3iss-" 
The  starch  could,  probably,  be  preserved,  in  this  solution,  as  a  permanent  micro- 
scopical specimen. 
1  tf=ten-thousandths  of  an  inch.  For  information  as  to  methods  of  measure- 
ment, the  works  on  microscopy  must  be  consulted.  Where  the  pharmacist  has  not 
access  to  them,  the  measurements  given  will  be  useful  to  him  by  indicating  the  rela- 
tive size  of  the  bodies  measured.  The  writer  uses  the  small  unit  tt.  so  that  fractions 
can  be  avoided,  and  the  comparison  of  length  can  be  made  readily,  without  reduc- 
tion. Fractions  of  inch  are  used  because  they  are  much  more  generally  used  and 
understood  in  this  country  than  millimeters. 
