440 
KELATION  OF  CHEMICAL  CONSTITUTION 
and  starch,  the  compound  ought  to  be  colloidal,  and  remain  in 
the  dialyser  ;  if,  on  the  contrary,  only  dissolved  iodine  and  hy- 
driodic  acid  were  there,  starch  would  alone  remain.  M.  Guichard 
made  a  great  number  of  experiments ;  he  remarked  that  iodine 
passed  the  dialyser  first,  then  hydriodic  acid  in  large  quantity  ; 
afterwards  the  iodide  became  suddenly  decolorized,  and  later  the 
iodine,  as  well  as  the  hydriodic  acid,  ceased  to  be  disengaged. 
When  the  experiment  was  made  with  iodide  of  starch  decolorized 
by  heat,  the  disengagement  of  iodine  was  difficult  to  perceive ; 
that  of  hydriodic  acid  was  alone  observed  ;  the  same  was  the 
case  with  the  iodide  heated  in  close  vessels  for  some  hours  to 
100°,  then  to  150°.  The  colorless  iodide  of  starch  has  then  no 
existence  ;  the  so-called  iodide  of  starch  is  simply  starch  tinted 
by  iodine.  Heat  thus  separates  the  iodine  from  the  starch ;  the 
iodine  then  remains  in  the  water,  either  as  such  or  as  hydriodic 
acid. — Lond.  Chem.  Neivs,  July  3,  1868. 
RELATION  OF  THE  CHEMICAL  CONSTITUTION  AND  PHY- 
SIOLOGICAL ACTION  OP  MEDICINE.  ADDITION  OP 
IODIDE  OP  METHYL  TO  VEGETABLE  ALKALOIDS. 
At  one  of  the  recent  meetings  of  the  Royal  Society  of  Edin- 
burgh, a  very  interesting  paper  was  read  by  Drs.  Crum,  Brown 
and  T.  R.  Fraser,  upon  the  influence  of  direct  chemical  addition 
upon  the  physiological  action  of  substances.  This  paper  is  the 
first  of  a  series  which  may  be  expected  to  throw  great  light  upon 
one  of  the  most  interesting  questions  which  can  suggest  them- 
selves, viz.,  the  relation  existing  between  the  chemical  constitu- 
tion and  the  physiological  action  of  medicinal  and  poisonous 
substances.  That  such  a  relation  must  exist,  we  can  have  no 
doubt ;  and,  indeed,  attempts  have  been  made  by  some  to  es- 
tablish the  relation  in  certain  cases.  Hitherto,  however,  the 
subject  has  not  received  that  systematic  investigation  which  it  is 
now  receiving  at  the  hands  of  the  authors  of  the  paper. 
In  order  to  arrive  at  any  accurate  knowledge  as  to  the  influ- 
ence which  chemical  constitution  exerts  upon  physiological 
action,  it  would  appear  to  be  desirable  to  take  substances  having 
a  very  definite  and  energetic  physiological  action,  and  then  to 
perform  upon  them  a  chemical  operation,  having  for  its  object 
