8.  Reduction  of  HbOg  by  Putrefying  Bodies.— Fill  a  test-tube  with  a  dilute
solution  of  oxy-hsemoglobin  or  blood,  add  a  drop  of  putrid  meat  infusion,  cork
the  vessel  tightly  to  make  it  air-tight,  and  allow  it  to  stand.  I'he  oxy-hoemo-
globin  is  reduced  to  hremoglobin,  the  colour  changes  to  i)urj)le-red,  and  the
Huid  shows  the  spectrum  of  h;vmoglobin.  A  better  plan  is  to  seal  up  the
blood  in  a  tube.  It  need  not  be  mixed  with  putrid  matter  in  order  to  observe
after  a  time  the  reduction.
9.  Haematinometer. — For  accurate  observation,  instead  of  a  test-tube  the
blood  is  introduced  into  a  vessel  with  parallel  sides,  the  glass  plates  being
exactly  i  cm.  apart  (fig.  31  D).     Study  this  instrument.
10.  Hgematoscope  (fig.  27). — By  means  of  this  instrum.ent  the  depth  of  the
stratum  of  fluid  to  be  investigated  can  be  varied,  and  the  variation  of  the
spectrum,  with  the  strength  of  the  solution,  or  the  thickness  of  the  stratum
through  which  the  light  passes,  at  once  determined.     Study  this  instrument.
11.  III.  Carbonic  Oxide-Hsemoglobin. — Through  a  diluted  solu-
tion of  oxy-haemoglobin  or  defibrinated  blood  pass  a  stream  of  car-
bonic oxide — or  coal  gas — until  no  more  CO  is  absorbed.  Note  the
florid  cherry-red  colour  of  the  blood.
D


50


PRACTICAL  PHYSIOLOGY.
[VI.
Dilute  the  solution  in  a  test-tube  and  observe  its  spectrum,
that  a  stronger  solution  is  required  than  with  HbOg,  to  show
the  absorption-bands.  Two  absorp-
tion-bands nearly  in  the  same  posi«
tion  as  those  of  HbOg,  but  very
sHghtly  nearer  the  violet  end  (fig.  24,
3).  Make  a  map  of  the  spectrum
and  bands.
