circumstances through mere habit although of no service. We have
combinations of this kind, at least in part, in the frantic gestures of
rage and in the writhings of extreme pain; and, perhaps, in the
increased action of the heart and of the respiratory organs. Even when
these and other emotions or sensations are aroused in a very feeble
manner, there will still be a tendency to similar actions, owing to the
force of long-associated habit; and those actions which are least under
voluntary control will generally be longest retained. Our second
principle of antithesis has likewise occasionally come into play.
Finally, so many expressive movements can be explained, as I trust will
be seen in the course of this volume, through the three principles
which have now been discussed, that we may hope hereafter to see all
thus explained, or by closely analogous principles. It is, however,
often impossible to decide how much weight ought to be attributed, in
each particular case, to one of our principles, and how much to
another; and very many points in the theory of Expression remain
inexplicable.
CHAPTER IV. MEANS OF EXPRESSION IN ANIMALS.
The emission of Sounds Vocal sounds Sounds otherwise produced Erection
of the dermal appendages, hairs, feathers, &c., under the emotions of
anger and terror The drawing back of the ears as a preparation for
fighting, and as an expression of anger Erection of the ears and
raising the head, a sign of attention.
In this and the following chapter I will describe, but only in
sufficient detail to illustrate my subject, the expressive movements,
under different states of the mind, of some few well-known animals. But
before considering them in due succession, it will save much useless
repetition to discuss certain means of expression common to most of
them.
_The emission of Sounds_. With many kinds of animals, man included, the
vocal organs are efficient in the highest degree as a means of
expression. We have seen, in the last chapter, that when the sensorium
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