not  great.  As  might  be  expected,  the  destruction  is  relatively 
smallest  when  the  concentration  of  the  red  blood  cells,  or  of  the  laked 
haemoglobin,  is  greatest,  and  when  the  concentration  of  haemoglobin 
is  very  low  the  destruction  may  be  very  nearly  complete  within  the 
period  of  experiment.  The  actual  figures  given  will  enable  some 
idea  to  be  formed  of  the  degree  to  which  in  blackwater  fever  the 
amount  of  haemoglobin  present  at  the  end  of  four  hours  represents 
the  amount  originall}'  present  in  the  urine  when  first  excreted.  Thus 
when  the  urine  originally  contained  5  per  cent,  of  red  blood  cells,  the 
percentage  at  the  end  of  four  hours  was  only  27  per  cent,  to  y2c,  per 
cent.,  35  per  cent,  to  47  per  cent,  of  the  haemoglobin  being  destroyed. 
W'hen,  however,  the  urine  originally  contained  0'33  per  cent,  of 
haemoglobin,  about  90  per  cent,  was  destroyed,  the  percentage  being 
reduced  to  0’03,  a  quantity  which  is  not  easily  recognised  or  estimated. 
The  percentages  in  the  Table  were  for  the  most  part  ascertained  by 
means  of  haemoglobinometer  readings.  The  original  concentrations 
were  made  up  by  means  of  the  haemocrit,  and  one  of  these,  as  a 
control,  was  measured  by  the  haemoglobinometer,  the  reading 
obtained  being  a  little  higher  (0‘5  per  cent.)  than  the  amount  given 
by  the  haemocrit. 
When  the  percentage  of  haemoglobin,  whether  in  the  form  of  red 
blood  cells  qr  of  dissolved  haemoglobin,  was  less  than  O’Oi  per  cent, 
in  the  urine,  at  the  end  of  four  hours  it  became  difficult  or  impossible 
to  recognise  oxyhaemoglobin  bands.  In  these  cases  the  urine,  which, 
as  already  mentioned,  had  acquired  a  brownish  tint,  gave,  on  slightly 
acidify'ing  and  heating,  a  brownish  white  jarecipitate  of  coagulable 
protein,  this  forming  in  many  cases  the  only  indication  of  the  original 
addition  of  haemoglobin. 
Owing  to  the  circumstance  that  urine  is  not  a  fluid  of  constant 
composition,  it  is  not  possible  to  calculate,  from  the  amount  present 
at  the  end  of  four  hours,  how  much  was  originally  present.  In  each 
individual  case  a  special  estimation  is  required.  Only  an  approximate 
idea  of  the  limits  of  the  range  of  destruction  in  different  concentra¬ 
tions  is  afforded  by  Table  25,  which,  however,  shows  that  with  a  high 
specific  gravity  of  the  urine  the  rate  at  which  destruction  proceeds  is 
increased.  Destruction  of  haemoglobin  was  usually  attended  with 
the  production  of  methaemoglobin,  which  was,  however,  present  only 
