Expression of the Emotions 433 
tarily 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.” This principle of anti- 
thesis has not been widely accepted. Nor is Darwin’s own position 
easy to grasp. 
“Our third principle,” he says?, “is the direct action of the excited 
nervous system on the body, independently of the will, and inde- 
pendently, 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 master- 
piece 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 dis- 
tinguished 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 bio- 
logical means of expression are full of subtle suggestiveness. Many 
modes of expression, otherwise useless, are signs of behaviour that 
1 Expression of the Emotions, p. 368. 2 Tbid. p. 369. 
D. 28 
