196 
AN  ESSAY  ON  SENNA. 
In  an  article  on  chrysophanic  acid,  (Amer.  Jour,  of  Pharm., 
vol.  xxx.  p.  442),  the  various  reactions  and  properties  of  this  vege- 
table principle  are  enumerated  ;  and  a  special  stress  is  laid  upon 
its  superior  solubility  in  benzole.  On  the  strength  of  these  ob- 
servations the  next  experiment  was  made. 
Exp.  III.  Two  ounces  of  senna  leaves,  powdered,  were  ex- 
hausted of  inert  resinous  matter  by  alcohol.  The  mass  was 
dried,  re-packed  in  the  instrument,  and  percolated  with  benzole. 
This  menstruum  passed  through  colorless,  and  after  spontaneous 
evaporation  left  no  residue.  The  mass  of  leaves  was  now  moist- 
ened with  very  dilute  sulphuric  acid,  dried  and  again  treated 
with  benzole.  The  result,  after  the  evaporation  of  the  benzole, 
was,  as  in  the  first  trial,  entirely  negative.  At  the  desire  of  Prof. 
Procter,  and  based  upon  the  volatility  of  crysophanic  acid,  the 
next  experiment  was  performed. 
Exp.  IV.  An  ounce  of  senna  leaves  was  carefully  dried  of 
adherent  moisture,  and  subjected  to  a  gentle  increasing  heat  in 
a  "  Mohr's  subliming  apparatus."  There  were  no  vapors  given 
off  until  the  heat  was  urged  sufficiently  to  char  the  drug,  when 
volumes  of  smoke  were  evolved ;  nor  was  any  deposit  formed  on 
the  condensing  cap,  except  finally  a  faint  film  of  carbon. 
Exp.  V.  Eight  ounces  of  leaves  were  exhausted  by  cold 
water,  the  infusion  evaporated  to  the  consistence  of  an  extract, 
first  by  rapid  boiling,  and  towards  the  close  by  a  more  moderate 
heat.  This  extract  proved  actively  cathartic  in  a  dose  of  24 
grains,  (equivalent  to  3i.  of  the  leaves),  thus  plainly  disproving 
the  assertion  so  frequently  made,  that  an  extract  does  not  repre- 
sent the  activity  of  the  drug,  owing  to  the  decomposition  of  the 
active  principal  by  heat.  The  cold  infusion  possessed  great 
aptitude  to  undergo  fermentation,  owing,  doubtless,  to  the  large 
proportion  of  glucose  present,  excited  by  the  presence  of  some 
vegetable  nitrogenized  principle,  like  albumen,  especially  as  the 
liquid  after  boiling  and  filtration  was  found  to  be  more  perma- 
nent. 
The  aqueous  solution  of  this  extract  of  senna  was  precipitated 
by  the  addition  of  liquor  plumbi  subacetatis,  and,  after  filtration, 
the  excess  of  lead  was  removed  by  a  current  of  HS.  ;  the  liquid 
was  filtered  and  evaporated  to  the  consistence  of  an  extract ;  this 
