In  none  of  the  foregoing  experiments  was  any  decrease  in  the 
amount  of  haemolytic  complement  observed  until  shortly  before  the 
death  of  the  animal,  with  the  single  exception  of  Experiment  i.  The 
seruni  of  this  guinea-pig,  which  was  infected  with  T.  brucei,  showed 
a  slight  decrease  in  complement  on  the  8th  and  nth  day  of  the 
disease.  The  blood  at  the  lime  contained  numerous  trypanosomes. 
In  Experiments  2,  5,  7  and  8  no  appreciable  decrease  of  the 
haemolytic  complement  occurred  during  the  course  of  the  disease,  even 
when  the  parasites  were  swarming  in  the  peripheral  blood  (i  to  every 
2  or  3  red  cells).  Many  estimations  of  the  complement  were  made  in 
the  different  experiments,  when  20-50  parasites  were  present  to  the 
microscopic  field  (Zeiss  objective  DD  ;  eyepiece  No.  4).  In  no  case  was 
any  diminution  noticed.  It  is  evident,  therefore,  that  the  presence  of 
numerous  trypanosomes  in  the  peripheral  blood  in  an  early  stage  of 
the  disease  does  not  necessarily'  result  in  a  diminution  of  the 
haemolytic  compl  em  en  t . 
On  the  othei  hand  in  a  late  stage  of  the  infection  shortly  before 
the  death  of  the  animal,  a  considerable  decrease  in  the  amount  of 
complement  was  observed  in  most  of  the  experiments.  On  five 
occasions,  Experiments  r,  2,  3,  9  and  12,  the  blood  of  animals  infected 
with  7.  br/icei  and  T.  evansi,  respectively,  contained  practically  no 
haemolytic  complement  a  few  hours  before  death.  In  other  cases, 
e.g.,  Experiments  6,  7,  13  and  15,  only  a  partial  diminution  could  be 
observed  in  the  serum  removed  just  before  the  death  of  the  animal, 
whilst  in  still  other  cases,  5.  to,  11,  14  and  16,  no  decrease  of  the 
haemolytic  complement  was  found  in  the  serum  withdrawn  about 
twelve  hours  before  death. 
From  these  observations  one  must  conclude,  therefore,  that  the 
diminution  of  the  complement  in  the  serum  of  animals  infected  with 
trypanosomiasis  is  simply  a  terminal  event,  and  does  not  occur  during 
the  earlier  stages  of  the  disease,  even  when  the  peripheral  blood  is 
swarming  with  parasites. 
The  following  experiments  were  performed  with  a  view  to 
ascertaining  whether  the  serum  of  infected  guinea-pigs  withdrawn 
a  few  hours  before  their  death  contained  any  body  which  had  the 
pioperty  of  inhibiting  to  any  extent  the  activating  power  of  the 
complement  of  normal  serum. 
