BLOOD.
does  not  coagulate  by  heat*.  When  thus  coagulated,
it  has  a  greyish  white  colour,  and  is  not  unlike  the
boiled  white  of  an  eggt.  If  the  coagulum  be  cut  into
small  pieces,  a  muddy  fluid  may  be  squeezed  from  it,
which  has  been  termed  the  serosity.  After  the  separation ¬
  of  this  fluid,  if  the  residuum  be  carefully  washed
in  boiling  water  and  examined,  it  will  be  found  to  possess ¬
  all  the  properties  of  albumen.  The  serum,  therefore, ¬
  contains  a  considerable  proportion  of  albumen.
Hence  its  coagulation  by  heat,  and  the  other  phenomena
which  albumen  usually  exhibits.
If  serum  be  diluted  with  six  times  its  weight  of  water, ¬
  and  then  boiled  to  coagulate  the  albumen,  the  liquid ¬
  which  remains  after  the  separation  of  the  coagulum, ¬
  if  it  be  gently  evaporated  till  it  becomes  concentrated, ¬
  and  then  be  allowed  to  cool,  assumes  the  form
of  a  jelly,  as  was  first  observed  by  De  Haent.  Consequently ¬
  it  contains  gelatine.
If  the  coagulated  serum  be  heated  in  a  silver  vessel,
the  surface  of  the  silver  becomes  black,  being  converted
into  a  sulphuret.  Hence  it  is  evident  that  it  contains
sulphur§,  and  Proust  has  ascertained  that  it  is  combined
with  ammonia  in  the  state  of  a  hydrosulphuret.
If  serum  be  mixed  with  twice  its  weight  of  water,
and,  after  coagulation  by  heat,  the  albumen  be  separated ¬
  by  filtration,  and  the  liquid  be  slowly  evaporated
till'it  is  considerably  concentrated,  a  number  of  crystals
are  deposited  when  the  liquid  is  left  standing  in  a  cool
place.  These  crystals,  first  examined  by  Rouelle,  consist ¬
  of  carbonat  of  soda,  muriat  of  soda,  besides  phos* ¬
  Fourcroy,  Ann.  de  Cbim.  vil.  157.
Ibid.  156.
§  Deyeux  and  Parmentier,  Jour.  de.  Phys.  xliv.  437.
1  Ibid.  157.
Bb2

387
Chap.  II.
ontans
albumen,
Geletine,
Sulphur,
Aat  as