298  Alexandria  and  India  Senna.  {Amjun"*ww?^ 
ALEXANDRIA  AND  INDIA  SENNA. 
v 
METHOD  OF  DISTINGUISHING  THEM  IN  POWDER. 
By  L.  E.  Sayre, 
Member  of  Research  Committee  C,  Revision  Committee  of  United  States 
Pharmacopoeia. 
The  question  of  distinction  and  identification  of  the  two  sennas, 
Alexandria  and  India,  was  the  subject  of  a  recent  preliminary  paper 
by  the  author.  Since  the  appearance  of  this,  more  careful  and  elabor- 
ate work  has  been  done  upon  the  same  subject,  the  results  of  which 
are  embodied  in  the  present  article.  Some  criticisms  having  been 
made  upon  this  early  work,  due  attention  will  also  be  paid  to  the 
disputed  points  in  the  endeavor  to  arrive  at  as  truthful  conclusions 
as  possible.  To  aid  in  this,  a  series  of  photomicrographs  have  been 
carefully  made,  and  are  here  reproduced.  The  accuracy  of  the 
drawings  may  be  the  subject  of  dispute,  owing  to  the  large  personal 
factor  that  enters  into  their  preparation,  but  the  appearances  shown 
by  a  photograph  admit  of  no  misconstruction,  provided  they  be 
truly  representative.  It  is  unnecessary  to  state  that  in  the  present 
instance  all  reasonable  precautions  have  been  taken  to  show  in  a 
few  reproductions  as  representative  appearances  as  could  be  found 
in  such  limited  areas.  As  contributing  to  a  truthful  understanding 
of  the  results  obtained,  a  brief  outline  of  the  methods  employed  is 
given,  and  this  is  followed  by  the  interpretations  and  conclusions. 
While  the  true  character  of  the  tissues  has  been  made  the  subject 
of  careful  study,  the  fact  has  constantly  been  borne  in  mind  that  the 
object  of  the  whole  matter  is  to  secure  a  simple  and  accurate  test 
for  senna  powders  that  shall  be  applicable  to  the  uses  of  those  for 
whom  it  is  intended.  It  has  been  recognized  that  no  one  feature  is 
found  constant  throughout  the  extent  of  the  leaf,  and  that  before 
any  appearance  can  be  pronounced  representative,  due  care  must  be 
exercised  by  taking  a  sufficient  number  of  observations.  It  is 
believed  that  all  precautions  have  been  taken  in  this  investigation, 
and  that  the  test  proposed  will  prove  reliable  and  sufficient. 
Methods. — The  photomicrographs  of  the  epidermis  were  made 
from  thin  sections  cut  directly  from  the  surface  of  the  leaf,  and  sub- 
jected to  no  more  treatment  than  was  necessary  to  mount  them  in 
plain  glycerin.  The  negatives  were  all  made  from  these  sections  in 
a  vertical  camera  of  fixed  length,  attached  to  a  Van  Heurck  micro- 
