INTRODUCTION. 9

would accompany an actual experience of the evil feared.
The destructive passions are shown in a general tension
of the muscular system, in gnashing of the teeth and
protrusion of the claws, in dilated eyes and nostrils,
in growls; and these are weaker forms of the actions
that accompany the killing of prey/5 Here we have,
as I believe, the true theory of a large number of expres-
sions; but the chief interest and difficulty of the subject
lies in following out the wonderfully complex results. I
infer that some one (but who he is I have not been able
to ascertain) formerly advanced a nearly similar view,
for Sir C. Bell says,9 " It has been maintained that what
are called the external signs of passion, are only the con-
comitants of those voluntary movements which the struc-
ture renders necessary." Mr. Spencer has also pub-
lished 10 a valuable essay on the physiology of Laughter,
in which, he insists on "the general law that feeling
passing a certain pitch, habitually vents itself in bodily
action; " and that " an overflow of nerve-force undirected
by any motive, will manifestly take first the most
habitual routes; and if these do not suffice, will next
overflow into the less habitual ones." This law I believe
to be of the highest importance in throwing light on our
subject.11

0 ' The Anatomy of Expression,' 3rd edit. p. 121.

10 ' Essays, Scientific, Political, and Speculative,' Second
Series, 1863, p. 111. There is a discussion on Lang-liter in
the First Series of Essays, which discussion seems to me
of very inferior value.

11 Since the publication of the essay just referred to,
Mr. Spencer has written another, on " Morals and Moral
Sentiments," in the ' Fortnightly Eeview,' April 1, 1871, p.
426. He has, also, now published his final conclusions in
vol. ii. of the second edit, of the ' Principles of Psychology,'
1872, p. 530. I may state, in order that I may not toe ac-
cused of trespassing on Mr. Spencer's domain, that I an-
nounced in my ' Descent of Man,' tha-t I had then written
a part of the present volume: my first MS. notes on the
subject of expression bear the date of the year 1838.

2