228  How  to  Distinguish  Viburnum  Barks.  {Am-/I°auyr;1^6arm' 
in  this  work,  that  I  have  been  unfortunate  in  being  unable  to  furnish 
them  with  authentic  material  to  work  upon.  The  material  collected 
by  the  chairman  of  the  sub-committee  taking  up  this  work  has  been 
only  sufficient  for  my  own  work ;  a  further  supply  has  not  as  yet 
been  received.  It  is  to  be  hoped  that  in  the  near  future  abundance 
of  material  will  be  had,  so  that  those  who  would  kindly  further  the 
investigation— verify  or  disprove  what  I  have  to  say — will  be  fur- 
nished with  reliable  samples.  To  those  whose  experience  is  quite 
limited  in  this  class  of  work,  who  desire  information  as  to  methods 
in  the  microscopic  examination  of  powders,  it  might  be  in  place  to 
say  a  word  or  two,  if  I  may  do  so  without  seeming  to  impart  infor- 
mation as  an  expert.  The  manipulation  necessary  to  the  examina- 
tion of  powders  is  quite  simple — not  at  all  complicated. 
The  manipulation  may  be  stated,  in  a  general  way,  as  follows : 
I.  Location  and  determination  of  elements  in  the  substance  in 
the  whole  state  by  study  of — 
(1)  Cross- section. 
Treat  with 
a,  Chlor-zinc  iodide ; 
b,  Haematoxylon ; 
c,  Methyl  violet,  etc. 
(2)  Longitudinal  section. 
II.  Study  of  comminuted  substance  : 
(1)  Seek  for  the  elements  revealed  in  the  section. 
(2)  Determine  which  elements  remain  most  firmly  adherent,  and 
which  separate  most  easily. 
(3)  Observe  cuticular  or  external  fragments,  shape  of  cells,  etc. 
(4)  Seek  for  external  appendages,  hairs,  etc. 
Those  who  are  familiar  with  the  above  reagents  know  that  they 
will  often  aid  in  identifying  in  the  powder  what  has  been  located  in 
cross  and  longitudinal  section.  The  same  reagents  used  in  both 
cases  will  act  the  same,  and  thus  identification  is  facilitated.  Before 
being  able  to  identify  drugs  in  the  powdered  condition  it  is  neces- 
sary to  fix  upon  some  feature  of  it  that  is  most  prominent  and  char- 
acteristic. In  the  case  of  leaves,  for  instance,  there  are  often  hairs 
and  glands  that,  in  their  form,  seem  at  once  to  distinguish  the  speci- 
men upon  which  they  occur.    As  an  example,  digitalis  may  be 
