14 
quinine  salt  was  tested  upon  red  blood  cells  freed  from  plasma,  the 
method  of  procedure  in  these,  and  most  of  the  succeeding  experiments 
of  the  same  type,  being  as  follows  :  — 
Method. — About  one  cubic  centimetre  of  blood  was  obtained  by 
pricking  the  finger,  previously  washed  and  cleansed  with  absolute 
alcohol,  and  allowing  blood  to  flow  drop  by  drop  into  a  small  glass 
collecting  tube  containing  a  measured  amount  of  a  i  per  cent,  solution 
of  potassium  oxalate  (containing  also  o'45  per  cent,  of  sodium  chloride, 
so  as  to  be  isotonic  with  the  red  cells),  in  the  proportion  of  one  part 
of  the  latter  to  from  four  to  ten  parts  of  blood.  The  mixture  thus 
obtained  was  next  sucked  up  into  a  graduated  2  c.cm.  pipette  and  its 
volume  noted.  The  percentage  (by  volume)  of  red  cells  contained  in 
the  mixture  was  then  determined  by  means  of  a  haemocrit.  The 
mixture,  or  a  measured  fraction  of  it,  was  next  added  to  about  10  c.cm. 
of  o'g  per  cent,  solution  of  sodium  chloride  and  centrifugalised  until 
the  red  cells  were  completely  precipitated.  The  supernatant  fluid 
was  then  pipetted  off  and  as  much  of  the  o'g  per  cent,  solution  of 
sodium  chloride  added  as  was  required  to  make  up  a  2' 5  per  cent, 
emulsion  of  red  cells.  In  many  of  the  experiments  a  portion  of  this 
emulsion  was  laked  by  the  addition  of  distilled  water,  and  the  amount 
of  haemoglobin  it  contained  determined  by  means  of  a  haemoglobino- 
meter  reading,  the  absolute  values  of  the  scale  of  the  instrument 
having  previously  been  determined  in  terms  of  the  red  cells  in  the 
moist  condition  of  one  of  us,  taken  as  a  standard.  In  this  way  the 
value  of  different  blood  emulsions  made  up  to  2' 5  per  cent,  of  wet  red 
cells  can  be  referred,  as  regards  their  haemoglobin  content,  to  the 
same  standard.  It  may  be  observed  that  sometimes,  as  for  example 
m  cases  of  malaria,  as  will  be  seen  later  (cp.  Table  24),  this  is 
absolutely  necessary  if  different  e.xperimental  results  are  to  be 
compared. 
The  red  blood  cell  emulsion  having  been  prepared  as  above 
described  measured  amounts  were  then  added  to  a  series  of  test-tubes 
containing  a  quinine  solution  isotonic  with  blood  plasma  and,  if 
necessary,  also  eg  per  cent,  of  sodium  chloride,  so  as  to  make  up  a 
diminishing  series  of  concentrations  of  quinine  salt,  while  at  the  same 
time  the  percentage  of  wet  red  cells  in  the  series  progressively 
increased  (Table  i).  In  this  way  the  point  was  determined  at  which 
the  red  blood  cells  present  were  completely  haemolysed  at  the  end 
