by a razor-like knife cause the least reaction, while a tearing,
crushing trauma causes the greatest response. It is a suggestive fact
that the greatest shock is produced by any technic which imitates
the methods of attack and of slaughter used by the carnivora.
_*In the course of evolution, injuries thus produced may well have
been the predominating type of traumata to which our progenitors
were subjected_. In one particular respect there is an analogy between
the response to trauma of some parts of the body of the individuals
of a species susceptible to shock and the response to trauma of the
individuals in certain other great divisions of the animal kingdom.
Natural selection has protected the crustaceans against their
enemies by protective armor, _e. g_., the turtle and the armadillo;
to the birds, it has given sharp eyes and wings, as, for instance,
the wild goose to another species--the skunk--it has given a noisome odor
for its protection. The turtle, protected by its armor against trauma,
is in a very similar position to that of the sheltered brain
of man and, like the brain, the turtle does not respond to trauma
by an especially active self-protective nerve-muscular response,
but merely withdraws its head and legs within the armored protection.
It is proverbially difficult to exhaust or to kill this animal by trauma.
The brain and other phylogenetically sheltered parts likewise give no
exhausting self-protective nerve-muscular response to trauma. The skunk
is quite effectively protected from violence by its peculiar odor.
This is indicated not only by the protective value of the odor itself,
but also by the fact that the skunk has no efficient nerve-muscular
mechanism for escape or defense; it can neither run fast nor can it
climb a tree. Moreover, in encounters it shows no fear and backs
rather than runs. The armadillo rolls itself into a ball for defense.
On these premises we should conclude that the turtle,
the armadillo, and the skunk have fewer nociceptors than has