2 7
Arranging the complements as far as possible in order of potency we get,
roughly :—
Guinea-pig
Rabbit
Goat
Man
Horse
Sheep
Do
He
...
...
...
...
...
...
...
...
...
...
...
...
...
...
...
...
...
...
...
...
...
...
...
...
...
...
....
.
...
...
...
...
...
...
...
...
...
...
...
...
...
...
...
...
...
. . .
..
...
. . .
...
...
...
. . .
. . .
...
...
..
. . .
...
...
. . .
. . .
...
...
...
...
. . .
...
...
. . .
1 0 0
46
43
34
2 3
1 1
1 1
Arranging the amboceptors as far as possible in order of potency, we get :—
Dog
...
Rabbit
...
Man
Goat
...
Sheep
Horse
..
Hen
...
Guinea-pig
...
...
..
...
...
.. .
...
...
...
..
...
...
...
...
...
..
...
...
...
...
...
. .
.
..
..
. . .
...
...
. . .
...
...
...
.
...
...
...
...
. . .
...
. . .
...
...
. .
...
...
. . .
.,,
...
...
. . .
. . .
.. .
...
...
..
. . .
. . .
...
...
. . .
...
. . .
100
65
6 0
48
48
18
18
6
Extended observations might change these arrangements considerably, but we
are probably justified in concluding that, of the serums tested, guinea-pig has most
complement and least amboceptor, and that dog has most amboceptor but
is comparatively weak in complement. As far as normal serums are concerned the
combination " dog-sensitizer + guinea-pig-complement " would probably prove to
be the most potent against a varied range of RBCs.
The facts that guinea-pig complement gives the most lysis with its own
corpuscles and that this lysis is most strongly marked with the more powerful
sensitizers, indicate that lysis of RBCs by their homogenous serums is merely a
matter of sufficient sensitization pins a sufficiency of complement. RBCs are
normally in a state of equilibrium with the complement contained in the serum
that surrounds them, and that serum contains no sensitizer for them. If highly
sensitized in a specific immune serum, RBCs are readily lysed by their own
complement ; and the reason that lysis in the series now under discussion was
either absent or incomplete is due to want of sufficient sensitization of the RBCs
by the normal heterogenous serums. Guinea-pig serum containing most comple-
ment was able to give a considerable degree of lysis with this insufficient sensiti-
zation, but all the others, which contain much less complement, fell far behind it in
this respect.
The conclusion is that, given a sufficient degree of sensitization, RBCs can be
lysed by homogenous complement. Given equal degrees of sensitization it may be
that RBCs are more resistant to homogenous than to heterogenous complements,
but this is an exceedingly difficult matter to prove experimentally, and, as far as
we know, there is no reliable experimental proof that any such difference of
resistance exists ; indeed there appears to be no particular reason why any
difference should be expected.
It might be thought that sensitization of RBCs in a large bulk of a normal
serum would enable them to fix enough amboceptor for complete lysis by their
homogenous serum, but in practice this is difficult to accomplish whatever the
reason may be. RBCs do not seem to be as avid of a normal amboceptor as
of an artificial amboceptor and, whereas it is easy to remove practically the
whole of an artificial amboceptor from a serum by digestion with the appropriate
RBCs, we have seldom succeeded in doing this in the case of normal serums.
It is possible that artificial and normal amboceptors do not obey the same laws
and that a condition of equilibrium between the amboceptor and the RBCs
obtains when a normal serum is used. As we have shown in another section
there is no equilibrium between the amboceptor in the fluid and the susceptible
RBCs in the case of immune serums, so that, even when the serum is diluted
ninety times, RBCs still pick out as much amboceptor as they do from the
undiluted serum.
For example, a sheep serum which was fairly rich in normal lysin for man,
rabbit and guinea-pig RBCs was used for sensitizing man, rabbit and guinea-pig
D- I