animal.
The _Cebus azar _,[511] when rejoiced at again seeing a beloved person,
utters a peculiar tittering (_kichernden_) sound. It also expresses
agreeable sensations, by drawing back the corners of its mouth, without
producing any sound. Rengger calls this movement laughter, but it would
be more appropriately called a smile. The form of the mouth is
different when either pain or terror is expressed, and high shrieks are
uttered. Another species of _Cebus_ in the Zoological Gardens (_C.
hypoleucus_) when pleased, makes a reiterated shrill note, and likewise
draws back the corners of its mouth, apparently through the contraction
of the same muscles as with us. So does the Barbary ape (_Inuus
ecaudatus_) to an extraordinary degree; and I observed in this monkey
that the skin of the lower eyelids then became much wrinkled. At the
same time it rapidly moved its lower jaw or lips in a spasmodic manner,
the teeth being exposed; but the noise produced was hardly more
distinct than that which we sometimes call silent laughter. Two of the
keepers affirmed that this slight sound was the animal s laughter, and
when I expressed some doubt on this head (being at the time quite
inexperienced), they made it attack or rather threaten a hated Entellus
monkey, living in the same compartment. Instantly the whole expression
of the face of the Inuus changed; the mouth was opened much more
widely, the canine teeth were more fully exposed, and a hoarse barking
noise was uttered.
The Anubis baboon (_Cynocephalus anubis_) was first insulted and put
into a furious rage, as was easily done, by his keeper, who then made
friends with him and shook hands. As the reconciliation was effected
the baboon rapidly moved up and down his jaws and lips, and looked
pleased. When we laugh heartily, a similar movement, or quiver, may be
observed more or less distinctly in our jaws; but with man the muscles
of the chest are more particularly acted on, whilst with this baboon,
and with some other monkeys, it is the muscles of the jaws and lips
which are spasmodically affected.
Cynopithecus Niger, in a Placid Condition. Fig.16-17
I have already had occasion to remark on the curious manner in which
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