66 
SENNA. 
name  of  "active  principle,"  inasmuch  as  it  is  quite  destitute  of 
activity,"  and  is  not  a  principle"  but  a  complex  mixture,  long 
passed  muster  as  the  so  much  desired  and  so  often  missed  senna 
cathartin ;  its  discovery  was  announced  in  1821.  Bley  and 
Diesel  pronounced  it  to  be  a  mixture  of  resinous  and  extractive 
matters  ;  they  might  with  truth  have  added  "  derived  partly  from 
senna,  partly  from  Cynanchum  ArgeV 
In  1845  a  prize  of  500  francs  was  offered  by  the  French,  for 
the  best  essay  on  the  chemistry  of  senna,  but  an  answer  not  being 
forthcoming,  the  offer  was  renewed  in  1857,  the  prize  being  in- 
creased to  1000  francs — still  no  response. 
In  the  same  year,  however,  Martius  gave  the  subject  his  atten- 
tion, and  pronounced  an  opinion  that  senna  owed  its  activity  to 
chrysophanic  acid,  a  body  of  very  stable  constitution,  and  in 
that  respect  very  unlike  what  might  have  been  expected  from 
senna.  Its  hitherto  acknowledged  sources  were  rhubarb  and  the 
lichen  Parmelia  parietina.  Martius  was  controverted  by  Sawicki, 
who  urged  the  little  solubility  of  the  acid.  Wiggers,  however, 
came  to  the  rescue  with  a  suggestion  that  the  combination  of  the 
acid  with  certain  bases  would  give  it  the  required  amount  of 
solubility  in  water. 
In  this  there  is  a  somewhat  near  approach  to  truth ;  Martius 
may  be  said  to  have  "burned,"  but  he  did  not  "touch"  the 
coveted  principle. 
Before  proceeding  to  the  analyses  of  senna,  published  within 
the  last  few  years,  I  will  refer  to  the  notions  of  the  ancients  as 
to  the  proper  modes  of  preparing  senna  for  administration.  It 
will  be  found  that  our  remote  predecessors  were  not  deficient  in 
the  power  of  observation,  whatever  what  might  have  been  their 
deficiencies  in  scientific  knowlege  ;  that  their  practice  if  not  their 
theory  was  correct.  Thus  the  Arabian  physicians  held  that  long 
boiling  impaired  its  activity,  so  did  Culpepper,  and  caution^  ac- 
cordingly. Heerlein,  a  modern  writer,  denies  this,  but  not  upon 
satisfactory  grounds.  Its  purgative  power  is  said  by  some  to  be 
increased  by  combining  with  the  senna  any  simple  bitter.  The 
infusum  amarum  purgans  and  the  mist,  gentianse  co.  owe  their 
origin  probably  to  this  idea.  It  might  even  throw  light  upon  the 
practice  (which  undoubtedly  was  not  of  modern  invention)  of 
