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