NOTE  ON  BLOOD-STAINS. 
439 
to  be  seen  by  reflected  light :  but  it  must  be  remarked  that 
it  is  not  reflected  directly  by  the  exterior  surface  of  the  liquid. 
It  proceeds  from  all  the  internal  points,  undergoes  a  multitude 
of  internal  reflections,  and  is  finally  refracted  on  its  exit  before 
reaching  the  eye. 
For  the  sake  of  accuracy,  it  is  necessary  to  substitute  in  place 
of  the  characteristic  phrase  of  MM.  Devergie  and  Gaultier,  of 
Claubry,  the  following  proposition: — The  sanguineous  liquid 
(obtained  after  re-dissolving  in  caustic  potash  the  coagulum  pro- 
duced by  heat),  if  observed  in  a  straight  tube,  appears  green 
when  placed  between  the  eye  and  the  sun,  and  reddish  if  the 
observer  is  placed  between  the  sun  and  the  tube. 
A  straight  tube  is  requisite,  because  if  a  flask  or  any  other 
vessel  of  a  certain  diameter  is  used,  the  liquid  appears  rose  co- 
lored under  all  circumstances.  If  a  half-filled  flask  is  shaken  the 
lower  portion  appears  rosy,  but  the  supernatant  froth  appears 
green.  In  a  full  flask,  seen  by  reflected  light,  the  whole  ap- 
pears rose  colored  ;  when  seen  by  transmitted  light  the  liquid 
contained  in  the  spherical  part  of  the  flask  always  appears  red  : 
whilst  that  in  the  straight  neck  appears  green.  It  is  astonish- 
ing to  observe  the  same  liquid  in  one  part  of  the  vessel  appear 
green  and  in  another  part  reddish.  These  variations  in  no  de- 
gree invalidate  the  certainty  of  the  conclusion  that  no  other 
substance  than  blood  unites  the  characteristic  successively  ob- 
served in  the  experiment,  namely: — 
1.  The  red  color  of  the  liquid. 
2.  Its  decoloration  and  coagulation  at  boiling  heat. 
3.  The  grey  color  of  the  coagulum,  and  its  complete  solubili- 
ty in  a  small  quantity  of  caustic  potash. 
4.  The  rose  color  of  the  alkaline  coagulum  seen  by  reflected 
light  in  a  straight  glass  tube,  and  its  green  color  under  trans- 
mitted light. 
5.  The  distinct  and  simultaneous  appearance  of  two  colors  in 
a  small  straight-necked  flask  when  the  quantity  of  liquor  is  large 
enough  to  admit  of  its  observation. 
All  this  is  without  prejudice  to  the  microscopic  observation 
of  spots  and  search  for  blood  globules,  which  constitute  the  es- 
sential characteristic  and  most  certain  indication  of  the  presence 
of  blood. — Chem.  New London^  June  2d^  1861, /rm  Journ.  de 
Pharm.  et  de  Chim, 
