Kingfishers, when they catch a fish, always beat it until it is killed;
and in the Zoological Gardens they always beat the raw meat, with which
they are sometimes fed, before devouring it.
We have now, I think, sufficiently shown the truth of our first
Principle, namely, that when any sensation, desire, dislike, &c., has
led during a long series of generations to some voluntary movement,
then a tendency to the performance of a similar movement will almost
certainly be excited, whenever the same, or any analogous or associated
sensation &c., although very weak, is experienced; notwithstanding that
the movement in this case may not be of the least use. Such habitual
movements are often, or generally inherited; and they then differ but
little from reflex actions. When we treat of the special expressions of
man, the latter part of our first Principle, as given at the
commencement of this chapter, will be seen to hold good; namely, that
when movements, associated through habit with certain states of the
mind, are partially repressed by the will, the strictly involuntary
muscles, as well as those which are least under the separate control of
the will, are liable still to act; and their action is often highly
expressive. Conversely, when the will is temporarily or permanently
weakened, the voluntary muscles fail before the involuntary. It is a
fact familiar to pathologists, as Sir C. Bell remarks,[120] that when
debility arises from affection of the brain, the influence is greatest
on those muscles which are, in their natural condition, most under the
command of the will. We shall, also, in our future chapters, consider
another proposition included in our first Principle; namely, that the
checking of one habitual movement sometimes requires other slight
movements; these latter serving as a means of expression.
CHAPTER II. GENERAL PRINCIPLES OF EXPRESSION _continued_.
The Principle of Antithesis Instances in the dog and cat Origin of the
principle Conventional signs The principle of antithesis has not arisen
from opposite actions being consciously performed under opposite
impulses.
We will now consider our second Principle, that of Antithesis. Certain
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