■^'^Feb.^S^''"'"}     Examination  of  Cascara  Sagrada.  89 
from  the  tenor  of  his  communication  we  should  conclude  that  he  had 
been  using  recent  bark.  In  the  same  journal,  1876,  p.  319,  there  is 
an  account  of  a  very  anomalous  behaviour  of  the  fresh  bark,  and  the 
statement  is  also  made  by  Fristedt  that  the  recent  bark  produces  colic 
and  vomiting.  We  have  already  indicated  the  cause  of  the  difficulty, 
and  believe  that  we  shall  shortly  be  able  to  explain  why  the  fresh 
bark  is  inefficient,  as  here  noted,  in  addition  to  producing  the  disa- 
greeable effects. 
The  existence  of  this  ferment  may  be  easily  demonstrated  to  the  sat- 
isfaction of  even  the  most  skeptical  investigator  in  a  very  simple  man- 
ner. A  cold  aqueous  percolate  from  four  ounces  of  the  bark  of  Rham- 
nus  purshiana,  to  the  pint,  is  divided  into  two  equal  portions,  and 
both  exactly  neutralized  with  sodium  bicarbonate.  One  portion  is 
now  to  be  boiled  or  exposed  in  a  flask  to  the  heat  of  boiling  water  for 
at  least  a  half-hour.  That  a  temperature  must  be  used,  capable  of  de- 
stroying this  ferment,  is  evident,  when  the  object  in  view  is  consid- 
ered. The  addition  of  a  little  yeast,  to  both  the  infusion  and  cooled 
decoction,  will  illustrate  the  matter  admirably.  In  the  decoction  the 
vinous  fermentation  alone  progresses,  while  in  the  infusion  a  gradual 
departure  from  neutrality  will  be  observed,  and  with  increasing  acidi- 
ty a  precipitation  of  the  resins,  previously  held  in  solution  as  sodium 
compounds. 
The  glucoside  referred  to  seems  to  be  peculiar  to  Rhamnus  purshiana, 
as  we  have  been  unable  to  determine  its  presence  in  the  frangula 
bark,  as  it  occurs  in  commerce.  This  glucoside,  though  having  very 
important  functions  and  properties,  has  hitherto  escaped  a  deserved 
recognition.  A  further  examination  of  the  fresh  bark  will,  we  think, 
confirm  the  existence  of  a  remarkable  difference  between  these  two 
barks,  inasmuch  as  experience  has  demonstrated  that  E,hamnus  purshi- 
ana exerts  a  decided  and  unmistakable  tonic  effect,  we  are  inclined  to 
ascribe  these  properties  to  the  bitter,  crystallizable  principle  already 
spoken  of.  Physiological  tests  to  determine  the  actual  properties,  not 
only  of  the  bitter  substance,  but  of  the  comparative  laxative  power  of 
the  different  resins,  are  under  way.  The  glucoside  may  be  obtained 
•  in  a  comparatively  pure  state  for  examination  by  precipitating  an 
aqueous  infusion  or  percolate  from  cascara  with  sub -acetate  of  lead. 
After  removal  of  the  excess  of  lead  by  H2S,  the  solution  exhibits  a  re- 
markable decomposition,  when  boiled  with  sulphuric,  hydrochloric,  or 
lactic  acid.    The  solution  becomes  intensely  bitter,  turbid  on  cooling. 
