270 
REMARKS  ON  SENNA. 
tongue.  When  exposed  to  the  light  it  promptly  begins  to  ac- 
quire color,  and  in  twelve  hours  becomes  of  a  delicate  wine  color 
of  a  rosy  tint.  From  this,  by  continued  exposure,  it  passes 
through  all  the  shades  of  reddish-brown  to  a  violet-black  by  re- 
flected light,  or  a  very  deep  brownish-red,  or  deep  garnet  by 
transmitted  light.  This  change  of  color  may  be — in  great 
measure,  at  least — delayed  at  any  point  by  seclusion  from  light, 
and  hence  the  lighter  or  darker  color  as  usually  met  with  is 
merely  an  indication  that  the  manufacture  has  put  it  up  in 
wrappers,  etc.,  sooner  or  later  after  distillation.  This  effect  of 
light  is  upon  the  impurities,  and  not  upon  the  phenols  themselves, 
all  of  these  being  colorless.  And  this  mixture  of  them  may,  by 
repeated  distillation,  which  is  within  easy  practical  reach  of  the 
large  manufacturer,  be  rendered  so  free  from  these  coloring  sub- 
stances that  any  ordinary  prolonged  exposure  only  produces  a 
wine  color  in  the  mixture.  This  condition  is  desirable,  and 
when  attained,  as  it  doubtless  will  be,  for  general  sales  and 
use,  the  practical  limit  of  useful  purification,  even  for  the  nicer 
medical  uses,  will  have  been  reached,  since  no  intrinsically  better 
substance  can  be  produced. 
(To  be  continued.)  | 
KEMARKS  ON  SENNA. 
By  T.  and  H.  Smith,  Edinburgh. 
We  have  read  with  great  interest  the  paper  on  "  Senna,"  con- 
tributed to  the  Pharmaceutical  Conference  by  Mr.  Groves,  and 
published  in  the  October  number  of  the  Society's  Journal.  The 
subject  is  important  and  interesting  in  itself,  and  the  novelty  of 
the  facts  stated,  and  the  information  yielded  as  to  the  real 
nature  of  the  cathartic  principle  of  the  drug,  must  draw  the 
attention  of  pharmaceutists  and  medical  men  to  its  value. 
The  interest  of  the  paper  was  enhanced  considerably  to  us, 
by  the  fact  that  we  had  spent  much  time  in  endeavoring 
to  isolate  the  purgative  principle,  and  obtain  it  in  a  form 
capable  of  producing  all  the  beneficial  physiological  action  of 
the  infusion,  unaccompanied  with  the  feelings  of  sickening  and 
