directly opposite
actions, whether or not these are of any use, under the excitement of
an opposite frame of mind."[170] This principle of antithesis has not
been widely accepted. Nor is Darwin's own position easy to grasp.

"Our third principle," he says,[171] "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."

Lack of space prevents our following up the details of Darwin's
treatment of expression. Whether we accept or do not accept his three
principles of explanation we must regard his work as a masterpiece of
descriptive analysis, packed full of observations possessing lasting
value. For a further development of the subject it is essential that
the instinctive factors in expression should be more fully
distinguished from those which are individually acquired--a difficult
task--and that the instinctive factors should be rediscussed in the
light of modern doctrines of heredity, with a view to determining
whether Lamarckian inheritance, on which Darwin so largely relied, is
necessary for an interpretation of the facts.

The whole subject as Darwin realised is very complex. Even the term
"expression" has a certain amount of ambiguity. When the emotion is in
full flood, the animal fights, flees, or faints. Is this full-tide
effect to be regarded as expression; or are we to restrict the term to
the premonitory or residual effects--the bared canine when the
fighting mood is being roused, the ruffled fur when reminiscent
representations of the object inducing anger cross the mind? Broadly
considered both should be included. The activity of premonitory
expression as a means of communication was recognised by Darwin; he
might, perhaps, have emphasised it more strongly in dealing with the
lower animals. Man so largely relies on a special means of
communication, that of language, that he sometimes fails to realise
that for animals with their keen powers of perception, and dependent
as they are on such means of communication, the more strictly
biological means of expression are full of subtle suggestiveness. Many
modes of expression, otherwise useless, are signs of