^^■j^^°j;'"-g^^arni.|        Actwe  Principle  of  Seyina  Leaves.  261 
in  water,  the  basic  salt  insoluble,  or  nearly  so,  and  on  treatment  with 
water,  the  former  splits  into  an  acid  and  basic  salt.  The  baryta  salt 
behaves  in  the  same  way.  When  in  mass  it  is  almost  black  in  color, 
but  when  finely  powdered  becomes  yellowish  red.  When  quite  pure 
neither  salt  contains  either  nitrogen  or  sulphur,  and  hence  the  presence 
of  these  bodies  in  Kubly's  cathartic  acid  must  be  attributed  to  impu- 
rities. If  the  salts  be  decomposed  with  sulphuric  acid  and  then  fil- 
tered, a  clear  brown  solution  of  the  free  acid  is  obtained.  The  test  for 
its  purity  consists  in  agitating  it  with  ether,  when  the  latter  should 
remain  quite  colorless.    It  is  almost  tasteless. 
Comparatively  few  experiments  were  needed  to  demonstrate  the 
physiological  action  of  cathartic  acid. 
A  solution  of  the  free  acid  was  carefully  neutralized  with  sodium 
carbonate,  and  a  portion  of  it  given  by  the  mouth  to  a  rabbit.  Within 
an  hour  very  violent  diarrho?a  occurred,  which  lasted  for  two  or  three 
hours,  at  the  end  of  which  time  the  animal  died.  Smaller  doses  caused 
simj)ly  violent  diarrh(»a.  The  urine  in  all  cases  gave  a  red  color  on 
the  addition  of  caustic  potash,  just  as  it  does  when  the  ordinary  phar- 
macopoeial  preparations  of  senna  leaves  have  been  administered. 
Post-mortem,  examinations  were  made  in  four  cases,  when  the  only 
changes  found  were  inflammation  and  hyper?emia  of  the  intestinal 
mucous  membrane. 
It  has  been  stated  that  the  senna  preparations,  when  injected  directly 
into  the  blood,  are  capable  of  causing  purgation,^  and  to  test  this  a 
series  of  experiments  was  made.  I  began  by  giving  small  doses  sub- 
cutaneously  and  by  the  jugular  vein,  but,  finding  them  without  efl^ect, 
increased  the  dose  given  until  it  was  twice  as  large  as  that  which  had 
caused  violent  diarrhoea  and  death  when  given  by  the  mouth.  In  no 
case  did  purgation  follow  the  administration.  The  animal  simply 
appeared  out  of  sorts  for  the  next  few  days,  probably  chiefly  from  the 
cflects  of  the  operation.  In  all  these  cases  the  urine  gave  the  caustic 
potash  reaction,  showing  that  the  cathartic  acid  had  become  decom- 
posed in  the  blood. 
The  investigation  of  the  chemical  relationships  and  decomposition 
products  of  cathartic  acid  ofi^ers  many  difficulties,  owing  largely  to  the 
instability  of  the  bodies  with  which  one  has  to  deal  and  to  the  small 
quantities  obtained. 
1  Compare  Nasse  "  Beitr.  zur  Physiologie  der  Darmbewegung,"  Leipzig, 
1866;  Wood  "  Treatise  on  Tlierapeutics,"  3d  edit.,  p.  464. 
