Natural Selection and Chemical Noci-association in the
Infections
Thus far we have considered the behavior of the individual
as a whole in his response to a certain type of
noci-influences. We have been voicing our argument in terms
of physical escape from gross physical dangers, or of
grappling
with gross nerve-muscular enemies of the same or of other
species. To explain these phenomena we have invoked the
aid of the laws of natural selection and phylogenetic association.
If our conclusions be correct, then it should follow
that in the same laws we may find the explanation of immunity,
which, of course, means a defensive response to our
microscopic enemies. There should be no more difficulty in
evolving an efficient army of phagocytes by natural selection,
or in developing specific chemical reactions against
microscopic
enemies, than there was in evolving the various nociceptors
for our nerve-muscular defense against our
gross
enemies. That immunity is a chemical reaction is no argument
against the application of the law of natural selection
or of association. What essential difference is there between
the chemical defense of the skunk against its
nerve-muscular
enemies and its chemical defense (immunity) against its
microscopic enemies?
The administration of vaccines becomes the adequate
stimulus which awakens phylogenetic association of a
chemical nature as a result of which immune bodies are
produced.
In discussing this subject I will raise only the question
whether or not the specific character of the inaugural symptoms
of some infectious diseases may be due to phylogenetic
association. These inaugural symptoms are measurably a
recapitulation of the leading phenomena of the disease in
its completed clinical picture. Thus, the furious initiative
symptoms of pneumonia, of peritonitis, or erysipelas, of the
exanthemata, are exaggerations of phenomena which are
analogous to the phenomena accompanying physical injury
and fear of physical violence. Just as the acute phenomena
of fear, or those which accompany the adequate stimulation
of nociceptors, are recapitulations of phylogenetic struggles,
so may the inaugural symptoms of an infection be a similar
phylogenetic recapitulation of the course of the disease. A
certain amount of negative evidence is supplied by a comparison
of the response to a dose of toxins with the response
to a dose of a standard drug. No drug in therapeutic dosage
except the iodin compounds causes a febrile response; no
drug causes a chill; on the other hand, all specific toxins
cause febrile responses and many cause chills. If a species
of animal had been poisoned by a drug during vast periods
of time, and if natural selection had successfully established
a self-defensive response, then the administration of that
drug would cause a noci-association (chemical), and a specific
reaction analogous to that following the administration of
Coley's toxins might be expected. Bacterial noci-association
probably operates through the same law as that through
which physical noci-association operates. Natural selection
is impartial, however. It must be supposed that it acts
impartially upon the microscopic invader and upon the host.
On this ground one must infer that, in accordance with the
same law of natural selection, the bacteria of acute infections
have met by natural selection each advance in the
struggle of the host for immunity. Hence the fast and
furious struggle between man and his microscopic enemies
merely indicates to what extent natural selection has developed
the
attack and the
defenserespectively. This
struggle is analogous to the quick and decisive battles of the
carnivora when fighting among themselves or when contending
against their ancient enemies. But when phylogenetically
strange animals meet each other, they do not
understand how to conduct a fight: natural selection has not
had the opportunity of teaching them. The acute infections
have the characteristics of being ancient enemies. On
this hypothesis one can understand the high mortality of
measles when it is introduced into a new country. By
natural selection, measles has become a powerful enemy of
the human race, and a race to which this infection is newly
introduced has not had the advantage of building up a
defense against it by the law of natural selection. May not
the phenomena of anaphylaxis be studied on associational
lines? Then, too, there may be chemical noci-associations
with enemies now extinct, which, like the ticklish points,
may still be active on adequate stimulation. This brief
reference to the possible relation of the phenomena of the
acute infections to the laws of natural selection and of specific
chemical noci-association has been made as a suggestion.
Since the doctrine of evolution explains all or nothing, I
have included many phenomena to see how reasonable or
unreasonable such an explanation might be.
