262 
DECOMPOSITION  OF  IODIDE  OF  STARCH,  ETC. 
altogether  superfluous;  since  starch  cannot  retain  the  iodine  in 
combination  with  it,  in  presence  of  the  digestive  fluids. 
The  iodide  of  starch,  in  the  form  of  paste,  has,  indeed,  been 
occasionally  recommended  as  one  mode  of  administering  the 
drug  ;  but  I  am  not  aware  that  the  mode  in  which  iodine,  in  this 
state  of  combination,  becomes  absorbed,  has  yet  been  directly 
investigated. 
The  solution  cf  starch  employed  in  the  following  experiments, 
was  made  by  boiling  five  grains  of  starch  in  the  ounce  of  water, 
and  allowing  the  fluid  to  cool.  The  experiments  were  all  made 
at  the  ordinary  temperature  of  the  atmosphere. 
1.  If  ^i  of  saliva  be  mixed  with  %\  of  iodine  water,  and  3ss 
of  the  starch  solution  added,  no  blue  color  is  produced;  but  a 
drop  or  two  of  nitric  acid  immediately  turns  the  mixture  blue 
and  opaque. 
gi  of  iodine  water  is  added  to  si  of  the  starch  solution,  ma- 
king an  opaque  blue  fluid  ;  oil  of  saliva  are  then  added,  and  the 
whole  shaken  up.  The  mixture  becomes  nearly  colorless  at  the 
end  of  five  minutes.  The  blue  color  is  then  restored  by  a  drop 
or  two  of  nitric  acid. 
2.  If  ~i  of  iodine  water,  with  Zi  of  starch,  be  mixed  with  an 
equal  quantity  of  fresh  pancreatic  juice  (from  the  dog)  the  blue 
color  is  entirely  dissipated  in  less  than  one  minute. 
3.  Light  yellow,  nearly  clear  bile,  from  the  dog's  gall-blad- 
der, destroys  immediately  the  blue  color  of  an  equal  quantity  of 
starch  and  iodine  water.  On  the  addition  of  nitric  acid,  the 
blue  color  is  restored,  modified  somewhat  by  the  green  tinge 
which  the  bile  takes  with  nitric  acid. 
4.  A  healthy  dog,  kept  for  24  hours  without  food,  was  killed 
by  section  of  the  medulla,  and  the  scanty,  light  yellowish,  frothy 
fluid  of  the  small  intestine  collected.  It  decolorized  immedi- 
ately the  blue  iodide  of  starch,  made  in  the  above  manner,  and 
the  blue  color  was  restored  by  nitric  acid. 
A  dog  was  kept  for  24  hours  without  food,  then  fed  with  fresh 
lean  meat,  and  killed  half  an  hour  after  feeding.  The  intesti- 
nal fluids  from  the  upper  half  of  the  small  intestine  acted  on 
the  iodide  of  starch  in  the  same  manner  as  in  the  last  experi- 
ment. 
5.  If  5ii  of  the  clear  yellowish  serum  of  the  blood  (horse's 
