CHAPTER XIV. CONCLUDING REMARKS AND SUMMARY.
The three leading principles which have determined the chief movements
of expression Their inheritance On the part which the will and
intention have played in the acquirement of various expressions The
instinctive recognition of expression The bearing of our subject on the
specific unity of the races of man On the successive acquirement of
various expressions by the progenitors of man The importance of
expression Conclusion.
I have now described, to the best of my ability, the chief expressive
actions in man, and in some few of the lower animals. I have also
attempted to explain the origin or development of these actions through
the three principles given in the first chapter. The first of these
principles is, that movements which are serviceable in gratifying some
desire, or in relieving some sensation, if often repeated, become so
habitual that they are performed, whether or not of any service,
whenever the same desire or sensation is felt, even in a very weak
degree.
Our second principle is that of antithesis. The habit of voluntarily
performing opposite movements under opposite impulses has become firmly
established in us by the practice of our whole lives. Hence, if certain
actions have been regularly performed, in accordance with our first
principle, under a certain frame of mind, there will be a strong and
involuntary tendency to the performance of directly opposite actions,
whether or not these are of any use, under the excitement of an
opposite frame of mind.
Our third principle is the direct action of the excited nervous system
on the body, independently of the will, and independently, in large
part, of habit. Experience shows that nerve-force is generated and set
free whenever the cerebro-spinal system is excited. The direction which
this nerve-force follows is necessarily determined by the lines of
connection between the nerve-cells, with each other and with various
parts of the body. But the direction is likewise much influenced by
habit; inasmuch as nerve-force passes readily along accustomed
channels.
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