AGf~ICULTURAL RESEARCH, PUSA.

32 PRACTICAL BACTERIOLOGY
one hour, it is seen that the vibrioi'> undergo progressive
lysis and disappear from the fluid. In this case the
complement of the blood plasma of the animal acts
along with thc antibody of the immune scrum.
Bactericidal action by a normal serum, in many
cases, is analogous to that produced by an immune
serum, and is dependent on a natural antibody
(vide supra) ancI complement. Normal bactcricidal
effects towards various Gram-positive bacteria are
independent of complement and are due to a thermostable
(5tjO C.) principle whosc exact natul'C is still
undetermined.
Haemolysis by a haemolytic antiserum is analogous
to bactcriolysis--i.e. it is due to a specific thermostable
antibody acting along with the normal complement.
Thus:
r Specific l .
Red Cells + \ antibody J + Complement = Haemolysls.
, r Specific \ N ff t
Red Cells + I antibody J = 0 e ec .
Red Cells + Complement =No effect.
The phenomenon of haemolysis by serum can be
demonstrated in vitro with blood suspensions and is
easily visible with the naked eye, the blood becoming
laked or transparent.
A suspension of red blood corpuscles in isotonic salt
solution plus the antiserum which has been heated
at 55° C. to annul complement (i.e. red cells + specific
antibody only) serves as a test for the presence or
absence of complement-e.g. in complement-fixation
tests-and is spoken of asa haernolytic systern (vide p. 35).
The opsonic effect of normal serum is produced
by a non-specific thermolabile principle, the norrnal
opsonin.
The increased opsonic action of an antibacterial sel'llm
has been regarded as clue to a specific thermostable
antibody (immune opsonin) which ean be differentiated
from the normal opsonin.