A  further  difference  between  the  haemolytic  agents  lies  m  their 
action  in  producing  a  further  change  in  the  haemoglobin  liberated 
from  the  red  cells.  Hydrochloric  acid  produces  the  most  marked 
effect,  rapidly  and,  in  the  stronger  solutions,  in  Table  6,  completely 
changing  the  liberated  haemoglobin,  so  that  a  brown  solution  results, 
which,  as  already  mentioned,  gives,  on  spectroscopic  examination,  no 
absorption  bands.  In  less  concentrated  solutions  the  appearance  of 
the  brown  coloration  is  less  marked,  but  continues  to  increase  when 
the  tube  is  kept.  Quinine  bihydrochloride  also  produces  the  same 
change,  especially  in  the  more  concentrated  solutions  which  were 
employed,  but  in  much  less  degree.  In  the  more  concentrated 
solutions  of  sodium  hydrate  also  the  brownish  coloration  is  produced. 
On  the  other  hand,  quinine  in  the  free  state  produces  little  change  of 
this  kind,  the  tubes  in  which  it  is  contained  not  turning  appreciably 
brown.  Moreover,  emulsions  of  red  blood  cells  laked  by  free  .quinine 
exhibit  little  difference,  as  far  as  the  haemoglobinometer  reading  is 
concerned,  from  emulsions  of  the  same  strength  laked  with  distilled 
water,  and  the  haemoglobin  set  free  from  red  blood  cells  by  alkaloidal 
quinine  changes  very  slowly  on  keeping,  so  that  the  haemoglobino- 
meter  reading  does  not  vary  during  the  period  of  three  hours  to  a 
degree  sufficient  to  vitiate  the  experiment,  as  is  the  case  with  the 
remaining  three  haemolytic  agents.  Quinine  bihydrochloride  was 
found  to  cause  the  appearance  of  a  relatively  small  amount  of 
methaemoglobin. 
A  third  point  of  considerable  interest  bearing  on  the  nature  of  the 
process  of  haemolysis  lies  in  the  amount  of  haemolysis  which  the 
different  concentrations  of  the  haemolytic  agents  are  capable  of 
producing.  Table  8  shows  that  the  weight  of  red  blood  cells 
completely  haemolysed  in  three  hours  by  quinine  bihydrochloride  is 
approximately  proportional  to  the  square  root  of  the  concentration, 
for  on  reference  to  Experiments  i,  2  and  3  it  is  seen  that  the  weight 
of  red  cells  is  10-4,  I5'6  and  36'4  that  of  the  quinine  salt,  while  the 
respective  concentrations  of  the  latter  are  0‘045  per  cent.,  o'iss  per¬ 
cent.  and  0-635  cent.  If  the  weight  of  red  blood  cells  completely 
haemolysed  were  exactly  proportional  to  the  square  roots  of  the 
concentration  of  quinine  salt,  the  first  figures  would  be  10-4,  i8'5  and 
39-3  respectively,  a  difference  which  is  well  within  the  range  of 
experimental  error.  For  the  concentrations  of  hydrochloric  acid  and 
