nd afterward put back it will not be attacked, while almost
invariably an ant belonging to another nest will be attacked.
It has been customary to use the words memory, enmity,
friendship, in describing this fact. Now Bethe made the
following experiment: an ant was placed in the liquids (blood
and lymph) squeezed out from the bodies of nest companions and
was then put back into its nest; it was not attacked. It was
then put in the juice taken from the inmates of a "hostile"
nest and was at once attacked and killed. Bethe was able to
prove by special experiments that these reactions of ants are
not learned by experience, but are inherited. The "knowing" of
"friend and foe" among ants is thus reduced to different
reactions, depending upon the nature of the chemical stimulus
and in no way depending upon memory.

Here, again, there is no essential difference between the common sense
and the scientific explanation of the behavior of the ant except so far
as the scientific explanation is more accurate, defining the precise
mechanisms by which the recognition of "friend and foe" is effected, and
the limitations to which it is subject.

Another result of the study of the comparative behavior of man and the
lower animals has been to convince students that there is no fundamental
difference between what was formerly called intelligent and instinctive
behavior; that they may rather be reduced, as has been said, to the
elementary form of reaction represented by the simple reflex in animals
and the tropism in plants. Thus Loeb says:

A prominent psychologist has maintained that reflexes are to be
considered as the mechanical effects of acts of volition of
past generations. The ganglion-cell seems the only place where
such mechanical effects could be stored up. It has therefore
been considered the most essential element of the reflex
mechanism, the nerve-fibers being regarded, and probably
correctly, merely as conductors.

Both the authors who emphasize the purposefulness of the reflex
act, and those who see in it only a physical process, have
invariably looked upon the ganglion-cell as the principal
bearer of the structures for the complex co-ordinated movements
in reflex action.

I should have been as little inclined as any other physiologist
to doubt the correctness of this conception had not