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dominant, and when a few feet from the shore she suddenly dived,
and emerged a good way farther out—only to repeat the process.
Here the external circumstances were such as to encourage conflict,,
but even so what are the most serious features of human conflict were
minimized by the outlet of alternate action.
Those who take up bird-watching as a hobby tend at first to be
surprised at the way in which a bird will turn, apparently without
transition or hesitation, from one activity to another—from fighting
to peaceable feeding, from courtship to uninterested preening, from
panic flight to unconcern. However, all experienced naturalists or
those habitually concerned with animals recognize such behaviour as
characteristic of the subhuman level. It represents another aspect of
the type of behaviour I have just been describing for the Red-throated
Diver. In this case, the internal state of the bird changes, presumably
owing to some form of physiological fatigue or to a diminution of in-
tensity of a stimulus with time or distance; the type of behaviour
which had been dominant ceases to have command over the mach-
inery of action, and is replaced by another which just before had been
subordinate and latent.
As a matter of fact, the prevention of conflict between opposed
modes of action is a very general phenomenon, of obvious biological
utility, and it is only the peculiarities of the human mind which have
forced its partial abandonment on man. It begins on the purely
mechanical level with the nervous machinery controlling our muscles.
The main muscles of a limb, for instance, arc arranged in two an-
tagonistic sets, the flexors bending and the extensors straightening it*
It would obviously be futile to throw both sets into action at the same
time, and economical when one set is in action to reduce to the
minimum any resistance offered by the other. This has actually been
provided for. The nervous connections in the spinal cord are so
arranged that when a given muscle receives an, impulse to contract,
its antagonist receives an impulse causing it to lose some of its tone
and thus, by relaxing below its normal level, to offer the least possible
resistance to the action of the active muscle.
Sherrington discovered that the same type of mechanism was
operative in regard to the groups of muscles involved in whole re-
flexes. A dog, for instance, cannot very well walk and scratch itself
at the same time. To avoid the waste involved in conflict between
the walking and the scratching reflex, the spinal cord is constructed
in such a way that throwing one reflex into action automatic-ally
inhibits the other. In both these cases, the machinery for preventing
conflicts of activity resides in the spinal cord. Although the matter