from  o'ooos  c.c.-0'005  c.c.  of  the  immune  serum  were  added  to 
]  c.c.  of  a  5  per  cent  suspension  of  well-washed  goat’s  red  cells. 
Afterwards,  i  c.c.  of  a  i  in  lo  dilution  of  normal  guinea-pig  serum 
was  added,  as  complement,  to  each  of  these  mixtures  of  amboceptor 
and  red  cells.  The  contents  of  each  of  the  tubes  was  then  made  up 
to  3  c.c.  by  the  addition  of  O'g  per  cent.  NaCl  solution.  It  was  found 
that  O'OOJ  c.c.  of  the  immune  serum  was  the  smallest  amount 
necessary  to  haemolyse  i  c.c.  of  a  5  per  cent,  suspension  of  goat's 
red  cells  in  from  10-15  minutes  at  37°  C. 
A  haemolytic  system  consisting  of  the  double  amount  of  the 
immune  serum  0'002  c.c.  and  i  c.c.  of  a  5  per  cent,  suspension  of 
goat’s  red  cells  was  employed  in  the  following  experiments. 
The  serum  of  infected  guinea-pigs  was  used  throughout  these 
experiments.  The  amount  of  complement  present  in  the  blood, 
withdrawn  from  one  of  the  veins  in  the  ear,  was  estimated  before 
injection,  and  the  guinea-pigs  were  then  inoculated  with  different 
strains  of  trypanosome.s,  e.g.,  T.  gambiense,  T.  equiperduni, 
T.  Irnicei  or  T.  evansi.  Subsequently,  examinations  of  the  amount 
of  haemolytic  complement  in  their  serum  w'ere  made  at  intervals  of 
two  or  three  days  during'  the  course  of  the  infection.  An 
observation  of  the  number  of  trypanosomes  in  the  peripheral  blood 
was  made  daily. 
In  Tables  I  and  II  the  results  obtained  with  the  serum  of 
guinea-pigs  infected  with  1.  bTucci  and  T.  evnusi,  respectively,  are 
recorded. 
Similar  results  w  ere  obtained  with  guinea-pig's  13  and  14  infected 
with  T.  ga^nbiense,  and  with  guinea-pigs  15  and  16  infected  with 
T.  cquipei'diun.  The  amount  of  haemolytic  complement  present  in 
the  serum  of  tliese  animals  was  examined  frequently  during  the 
period— between  three  and  four  and  a  half  months— which'’ they 
lived  after  infection.  At  no  time  was  any  diminution  of  the 
complement  observed  until  a  few  hours  before  the  animal’s  death, 
when  a  jiartial  disappearance  of  complement  was  noticed  in  animals 
13  and  15.  There  was  no  appreciable  loss  of  complement  observed 
in  guinea-pigs  14  and  16  in  the  serum  removed  about  twelve  hours 
before  their  death.  At  no  time  did  their  blood  exhibit  more  than 
one  or  two  trypanosomes  to  a  field,  and  frequently  none  were  seen  after 
a  careful  search. 
