7^ 
having  been  determined  m  terms  of  the  red  cells  (in  the  moist 
condition)  of  one  of  us  taken  as  a  standard. 
When  healthy  human  blood  was  collected  m  the  manner  above 
described,  the  plasma  was  found  to  be  light  orange  coloured  and  to 
present  no  trace  of  a  red  tint  in  a  tube  of  about  5  mm.  internal 
diameter.  If  examined  by  the  spectroscope  in  a  column  18  mm.  high, 
o.xyhaemoglobm  bands  were  always  found,  not  unficPjuently,  it  is  true, 
on  the  threshold  of  visibility.  When  matched  with  a  solution  of 
haemoglobin,  the  amount  present  was  represented  by  percentages  of 
Table  31.  Exammation  of  oxalatcd  blood  plasma,  for  the  presence  of  dissolved  haemo- 
globirij  in  healthy  raen. 
No.  of 
Obser¬ 
vation 
Contlition  of  subject 
supplying  plasma 
Amount 
of  blood  : 
amount  of 
potassium 
oxalate 
solution 
Colour  of  oxalated 
plasma  in  a  layer 
3  mm.  thick 
r 
Healthy  . 
4  :  1 
Orange 
z 
„  (twelve  days  later) 
Orange 
3 
„  (nine  months  later) 
Light  orange 
4 
llealtliv 
M 
Light  orange 
5 
„  (one  day  later) 
Light  orange 
6 
„  (seven  days  later)  ... 
,, 
Light  orange 
7 
Healthy  . 
11 
Light  orange 
Length  of 
column 
examined 
with 
spectroscope 
Percentage  of 
haemoglobin 
in  the  blood 
plasma 
18  mm. 
0-^5  % 
°’i3% 
11 
o’'5% 
0-10% 
O' >3% 
11 
0-13% 
0-10% 
red  cells  ranging  from  0-25  per  cent,  to  O'lO  per  cent,  or  less  (Table 
31).  When  the  serum  is  light  orange  in  colour  the  limit  of  visibility 
of  the  oxyhaemoglobin  bands,  it  may  be  observed,  is  in  a  column 
18  mm.  high  about  0'02  per  cent,  in  daylight  of  moderate  intensity. 
The  haemoglobin  present  was  not  due  to  the  red  blood  cells  having 
been  incompletely  removed  by  centrifugalisation,  for  microscopical 
examination,  aided  by  further  centrifugalisation,  failed  to  reveal  the 
presence  of  red  cells,  while  in  concentrations  of  O’  i  per  cent,  or  more, 
due  to  the  presence  of  red  cells,  the  plasma  was  obviously  turbid  to 
the  naked  eye,  and  when  examined  with  a  hand  lens  red  cells  were 
readily  seen  in  fair  abundance.  On  the  other  hand,  it  is  clear  that 
the  amount  of  haemoglobin  present  is  dependent  to  some  extent 
upon  the  technique,  for  if  two  samples  of  blood  are  withdrawn  from 
the  finger  in  succession,  the  intensity  of  the  bands  in  the  plasma 
will  be  found  as  a  rule  to  exhibit  some  variation,  which  is,  however, 
