_Anthropopithecus_, De Blainville, Leçons Orales (1839).
_Troglodytes_ (nec V.), Geoffr., Ann. Mus., xix., p. 87 (1812).
{188}This genus contains those Apes which stand highest, next to Man, in
the animal kingdom. This proximity, however, refers only to his external
conformation and his anatomical structure.
The Chimpanzees approach very closely to the Gorilla in structure. Indeed
the Gorilla was at first placed in the same genus as the Chimpanzee, which
was much earlier known to science than its larger cousin, although an
excellent description of the Gorilla, under the name of Pongo, was brought
to this country by Andrew Battell, an English prisoner of the Portuguese in
Angola, early in the seventeenth century, and published in "Purchas his
Pilgrimage," in 1613, a story which for the first time referred definitely
to the Chimpanzee.
The body is heavily built, but shorter and less robust than that of the
Gorilla. The crown is depressed, and the supra-orbital ridges, from which
rise stiff strong eye-brows, are prominent, but not remarkably so. The
eye-lids are wrinkled, and their margins set with eye-lashes. The nose, of
which the ridge is shorter than in the Gorilla, is depressed in the middle,
flatter at the extremity, and, as in the last-named species, is furrowed
longitudinally, its nostrils looking more downward and forwards. The lips
are extremely mobile and protrusile, the upper one broad and the lower one
retreating from the mouth, and not forming a true human-like chin, though
it is more prominent than in the Orang. The cheeks are more wrinkled than
in that Ape. The ears are large and projecting from the side of the head,
and often carry a lobule. They are strangely like those of Man, and, as Mr.
Darwin has remarked, the Chimpanzee never moves or erects its ears, so that
they are equally rudimentary, as far as that function is concerned, as in
Man. The shoulders and chest are broad, and indicate great strength. Their
lower limbs are longer in proportion than in the Orang. {189}The foot,
which is anatomically in no respect a hand, is sometimes shorter than the
latter, the great-toe is thick, opposable, and thumb-like, the other four
toes are united together by a web, the heel is somewhat developed, and the
whole of the sole of the foot is applied to the ground when walking. The
arms, of which the humeral segment is about equal in length to the
fore-arm, are long, but reach only a little below the knee--their span
being about a half more than the height of the body. The hands, which are
wonderfully human in form, are broad, comparatively short, and less
hook-like than in the Orang. The hair on the arm and fore-arm converges
towards the elbow, as in the Gorilla and Orang. The thumb is short in
comparison with the same digit in Man, and, as in the human hand, the
middle finger is the longest; the outer four fingers being united by a web
reaching up to the first joint. The palm of the hand can be applied flat to
the ground; but though the Chimpanzees can stand or run erect on the flat
sole of the foot, they prefer to advance leaning forward, supporting
themselves on the knuckles of the hand. They have no callosities on the
ischiatic bones, on which they sit.
The female Chimpanzees are slightly smaller than the males, but the
disparity between them is much less than between the two sexes of the
Gorilla. The nose and teeth are less prominent, and the belly is more
tun-shaped. The young males also exhibit fewer differences from the adult
than among the Gorillas, though differing in many points of their soft
anatomy and osteology. The nose lengthens, and its extremity widens, while
the face becomes more prognathous with increasing years. In the young the
frontal bone is low and flat. The skull in the Chimpanzee is elongated, and
small in proportion to the body; the forehead is smaller, the crown more
rounded than {190}in the Gorilla, and the back of the head convex.[2] The
central (sagittal) crest, so strongly developed in the Gorilla and the
Orang, is here wanting; the supra-orbital ridges which extend across the
face, and the occipital prominences for the back-muscles, though large, are
also less marked. The orbits have a circular rim, and are less prominent
than in the Gibbons. The nasal bones are but slightly arched, and the
openings for the nostrils round and small. The jaws, which are smaller,
proportionately to the cranium, in this genus, than in any other of the
_Simiidæ_, protrude far forward, but the symphysis of the lower jaw is
smaller than in the Gorilla, and its two halves low and wide. The bones of
the skull are much hollowed out into cavities (sinuses) in the forehead,
nose, and jaws, all of which communicate with each other. The plane of the
_foramen magnum_ (for the passage of the spinal cord) is oblique to the
plane of the base of the skull.
The volume of the cranium is from twenty-six to twenty-seven cubic inches,
or about one-half of the lowest capacity of a normal human cranium. A
styloid process is more or less distinctly visible in the Chimpanzees.
The canine teeth are long and conical, but less than in the Gorilla; and
the diastema, or gap, between them and their neighbouring teeth is smaller
than in the other Apes. The molar teeth are four-cusped, and have the
oblique ridge already described extending from the front inner to the hind
outer cusp; and the middle lower molar has five cusps, both these dental
characters being similar to those in Man. The anterior lower pre-molar,
however, is pointed, and has a long sharp anterior edge, as in the
_Cercopithecidæ_.
{191}The vertebral column begins to show the S-shaped flexure,
characteristic of Man's back-bone; it presents also a human character in
the form of its second neck vertebræ, and there are thirteen pairs of ribs,
as in Man. The hindmost vertebræ "give the impression of a rudimentary
tail." (_Hartmann._)
The humerus is nearly equal in length to the fore-arm; the wrist (_carpus_)
has only eight bones (the central bone being absent), agreeing, therefore,
with the number in Man.
All the ridges and grooves seen in the human brain are present in that of
the Chimpanzee, but "they are simpler and more symmetrical, and larger in
proportion to the brain." (_Huxley._) The cerebellum, and the nerves also,
are larger in proportion to the cerebrum than in Man; and certain
structures (the _corpora trapezoidea_) which exist in the brains in the
lower Mammalia are absent. These prominences, which are situated in that
portion of the brain known as the _medulla oblongata_, at the summit of the
spinal cord, disappear, as we have seen, in all the genera of higher rank
than the _Cebidæ_, one of the lowest families of the _Anthropoidea_. The
brain in its convolutions and in many other respects conforms to that of
the Orang. This is especially the case in _A. calvus_.
The uvula, which is absent in the throat of the Orang, is pendulous in the
Chimpanzees, as in Man. Large air-sacs are also present, and the hyoid bone
is excavated posteriorly, suggesting the conformation of the same bone in
_Alouatta_ (the South American Howlers). The stomach is very similar to
that of Man, and so are the digestive and reproductive organs. The round
ligament, attaching the head of the thigh-bone into its pelvic socket, is
present, and restricts the flexibility of the hind-limb of the Chimpanzees,
compared with that of {192}the Orang. Its presence, however, while acting
somewhat less favourably in regard to the climbing capacities of these
animals, whose habits are less essentially arboreal than the Orangs',
beneficially assists them in walking, affording them a firmer support on
the ground. In the Chimpanzee there is always a semi-lunar fold (_plica
semilunaris_) in the inner corner of the eye, corresponding to the
nictitating membrane (or third eyelid) of birds. In some of the Lemuroids
it is well developed (_suprà_, vol. i., p. 90), and is large in some races
of men.
The Chimpanzee is confined to the West African Sub-region, as defined by
Dr. Bowdler Sharpe. It is known from Loango, along the banks of the Upper
Congo, and Mr. Monteiro (P. Z. S., 1871, p. 544) says it is quite unknown
to the south of the Congo; it also occurs throughout the country of the
Manyema, in Central Africa, where Livingstone describes it under the name
of Soko; and southward as far as 10° south latitude, to Lake Moero.
Schweinfurth has recorded it from the Niam-niam country.
The Chimpanzees inhabit forest regions, and feed on wild fruits in the
woods, and the products of cultivated gardens, not rejecting, when they can
capture it, animal food. They live in separate families, or in limited
communities of small families mixed together, but each male lives with his
own single female. They are more arboreal than the Gorilla, but much less
so than the Orangs. In many districts they seem to live on the ground.
They emit loud cries, shrieks, and howls in the morning and evening, and
often during the night. "Since they are really accomplished in the art of
bringing forth these unpleasant sounds, which may be heard at a great
distance, and are reproduced by the echoes, it is impossible to estimate
the number {193}of those who take part in the dreary noise, but often we
seemed to hear more than a hundred." (_Pechuel-Lösche._) These Apes also
build resting-places, not far from the ground, like the Orangs, composed of
twigs and sticks on the branch of a tree or a crotch, in which the female
and her young take refuge for the night, the male placing himself on guard
beneath.
They seldom make an unprovoked attack on the natives wandering in the
forest; on the contrary, they are peaceably disposed animals, glad to get
out of the way of danger or possible enemies. Yet, when pressed, they form
no mean antagonist. Biting is their principal mode of defence.
"As seen here," says Savage, "they cannot be called gregarious, seldom more
than five or ten at most being found together. It has been said on good
authority, that they occasionally assemble in large numbers in gambols. My
informant asserts that he saw once not less than fifty so engaged, hooting,
screaming, and drumming with sticks upon old logs, which is done in the
latter case with equal facility by the four extremities.... When at rest,
the sitting posture is that generally assumed. They are sometimes seen
standing or walking, but when thus detected, they immediately take to all
fours, and flee from the presence of the observer. Such is their
organisation that they cannot stand erect, but lean forward. Hence they are
seen, when standing, with the hands clasped over the occiput, or the lumbar
region, which would seem necessary for balance or ease of posture."
Most of the accounts of the habits we have of Chimpanzees, refer to those
of young individuals kept in captivity. There is still much to be
discovered as to the ways and modes of life of the adults of both the
Chimpanzee and the Gorilla. They are both very delicate, and in temperate
climates rarely live {194}more than a few months; a Bald Chimpanzee (_A.
calvus_), however, survived five years in the Zoological Gardens, in
London.