and in part to the nakedness of their eyebrows, of which the movements
are thus rendered less conspicuous. When, however, they raise their
eyebrows their foreheads become, as with us, transversely wrinkled. In
comparison with man, their faces are inexpressive, chiefly owing to
their not frowning under any emotion of the mind that is, as far as I
have been able to observe, and I carefully attended to this point.
Frowning, which is one of the most important of all the expressions in
man, is due to the contraction of the corrugators by which the eyebrows
are lowered and brought together, so that vertical furrows are formed
on the forehead. Both the orang and chimpanzee are said[518] to possess
this muscle, but it seems rarely brought into action, at least in a
conspicuous manner. I made my hands into a sort of cage, and placing
some tempting fruit within, allowed both a young orang and chimpanzee
to try their utmost to get it out; but although they grew rather cross,
they showed not a trace of a frown. Nor was there any frown when they
were enraged. Twice I took two chimpanzees from their rather dark room
suddenly into bright sunshine, which would certainly have caused us to
frown; they blinked and winked their eyes, but only once did I see a
very slight frown. On another occasion, I tickled the nose of a
chimpanzee with a straw, and as it crumpled up its face, slight
vertical furrows appeared between the eyebrows. I have never seen a
frown on the forehead of the orang.
The gorilla, when enraged, is described as erecting its crest of hair,
throwing down its under lip, dilating its nostrils, and uttering
terrific yells. Messrs. Savage and Wyman[519] state that the scalp can
be freely moved backwards and forwards, and that when the animal is
excited it is strongly contracted; but I presume that they mean by this
latter expression that the scalp is lowered; for they likewise speak of
the young chimpanzee, when crying out, as having the eyebrows strongly
contracted. The great power of movement in the scalp of the gorilla, of
many baboons and other monkeys, deserves notice in relation to the
power possessed by some few men, either through reversion or
persistence, of voluntarily moving their scalps.[520]
_Astonishment, Terror_ A living fresh-water turtle was placed at my
request in the same compartment in the Zoological Gardens with many
monkeys; and they showed unbounded astonishment, as well as some fear.
This was displayed by their remaining motionless, staring intently with
widely opened eyes, their eyebrows being often moved up and down. Their
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