_Monkeys._--3. Mona (Cercopithecus mona); 4. Howler (Mycetes); 5.
Spider (Ateles).]
11. The QUADRUMANA (fig. 72), so called from their hind and
fore feet both having thumbs, and being developed into hands, includes
the Monkeys; they may be divided into two tribes, those inhabiting
the Old World (Simiidæ), and those inhabiting the New (Cebidæ),
these include what were formerly called Apes, Baboons, &c. These
animals approach the most nearly to the form of the human being, the
Chimpanzee being considered the nearest in formation to Man; there are,
however, many very broad distinctions between the two, especially in
the foot and head. The Quadrumana are very clever, but their actions
seem to have more meaning in them than they in reality possess, owing
to the resemblance of these creatures to the human being. There
are many surprising accounts of these beings, such as their arming
themselves with sticks and stones to defend themselves; but no act of
reason has ever yet been perceived in them, nor any tendency towards
improvement, except that which has been given them by Man. "The Monkey
who had seen the world," and went home and taught his companions, is
a fable in both senses of the word. The Monkey tribe are formed to
pass their lives in the trees among the branches, their hands being
formed to suit this kind of life. None of them walk well, but when
they are among the branches, swinging themselves from bough to bough,
few creatures are more active; their food is fruit and nuts of all
kinds. The Chimpanzee, certainly, is the nearest approach to Man in
the lower animals, and walks better in an upright position than does
the Ourang-outang, whose whole life is spent in the trees, while the
Chimpanzee often inhabits holes in the earth and rocks. In the "Penny
Cyclopædia" is the following account of one, by Captain Payne:--
"It shook hands with some of the sailors, but refused its hand with
marks of anger to others, without any apparent cause. It speedily,
however, became familiar with the crew, except one boy, to whom it was
never reconciled. When the seamen's mess was brought on deck it was
a constant attendant, would go round and embrace each person, while
it uttered loud yells, and then seat itself among them to share the
repast."
Some of the Monkey tribe (the Spider-monkeys) have the power of holding
fast with the end of the tail; it, in fact, forms a sort of hand,
and they swing from the boughs by it, and it is said that several
will attach themselves in this way, forming a long chain, and swing
themselves from the topmost bough of a tree when they wish to cross a
stream, the lowest catching hold of the boughs on the opposite side,
and the uppermost of them letting go his hold, they are all thus
conveyed across.
12. BIMANA (two-handed). This order includes Man alone. Man
has been placed in a separate class, and not as the first order of
the Mammalia, but, as will be presently noticed, although he has many
attributes which no other animal has, yet in bodily construction, and
all the functions of his material part, he so nearly resembles the
other orders of his class that it is deemed better to place him at
their head under the designation of "two-handed;" although indeed he is
the only animal who can be said to possess hands, properly so called,
for those of the Monkey tribe are so imperfectly developed that they
have but little claim to the name.
In his circulation, respiration, digestion, &c., Man exactly resembles
the other Mammalia, also in the organs of locomotion and special sense,
modified slightly in form; but to these purely animal attributes, he
has superadded faculties which raise him above them, and show him to
be the last and most perfect of God's creatures, one step further, in
fact, than any other living being; and it is a curious circumstance,
and one showing the accuracy of detail, with which the Mosaic account
of Creation in the Bible abounds, that this very superiority is not
only mentioned in many ways, but recorded as the result of a special
act of God over and above his formation as an ordinary animal, in
which state he was created, for we find the words, "and breathed into
his nostrils the breath of life, and man became _a living soul_,"
this especial act was not performed for any other being which God had
created, of which it is stated simply "male and female created He them."
Man is possessed of sentiments (or those feelings which prompt him to
believe in, look forward to, and hope for a higher state of existence,
than that which he enjoys here) which none of the lower animals
have, and of reason in place of instinct. There is certainly a vast
difference between the two, although many would have us believe the
one is the same as the other, but of a higher order; instinct causes
its possessor to act from innate impulse without consciousness of the
result, while reason points out "the why and the wherefore." Man is
conscious of his own identity, this is also peculiar to him; moreover,
all the performances of man can be improved by practice, none of the
instincts can, but are as perfect at first as at last; the Bee makes
the comb, and the Bird the nest, as well the first time as the last,
and although the higher animals, as the Dog, Horse, Elephant, &c., can
be taught to perform various clever and useful acts, yet it is by
Man's instrumentality and not by their own powers; in fact there is not
an animal which left to itself has the slightest power within itself
of deviating one iota from those peculiar instincts which were given
it by God. But Man at every effort rises higher than he was before,
till he arrives at such a knowledge of the great works and designs
of his Creator that he bows his head in awe and admiration of the
wonders permitted to appear to his comprehension. With respect to his
bodily structure, Man undoubtedly stands first in the race of beings,
although, in some particulars, such as the acuteness of the senses, he
may be inferior to some.
[Illustration:
_a._ Skull.
_b. b._ Vertebral column or Spine.
_c._ Ribs.
_d._ Sternum or Chest bone.
_e. e._ Scapulae or Blade bones.
_f. f._ Clavicles or Collar bones.
_g. g._ Pelvic or Hip bones.
_h. h._ Humeri or Arm bones.
_i._ Radius }
} Bones of fore-arm.
_j._ Ulna }
_k._ Femur or Thigh bone.
_l._ Tibia or Large bone of leg.
_m._ Fibula or Small bone of leg.
_n._ Calcaneum or Heel bone.
_o._ Tarsal bones or Bones of the
foot.
_p._ Carpal bones or Bones of the
wrists.
FIG. 73.--THE HUMAN SKELETON.]
The Human frame consists of a skeleton (fig. 73) formed of hard
and unyielding bone, having joints to admit of motion in certain
directions; this skeleton performs certain great and important offices,
it forms strong boundaries or protecting cases for most of the vital
parts, so as to shield them from external violence, such as the brain
and spinal cord, the lungs, heart, &c., it also furnishes a series of
levers to be acted on by the muscles, for the purposes of motion, and a
firm support for the soft parts of the system. The skeleton is divided
into the head, trunk, and extremities; the head is again divided into
cranium and face; the trunk is divided into spine, thorax, and pelvis;
the extremities into the upper and lower, the upper consisting of arm,
fore-arm, and hand; the lower of thigh, leg, and foot. The bones are
divided into "flat bones" (fig. 74) and "long bones" (fig. 75), the
flat bones (as a general rule) form the boundaries of the cavities, and
the long bones the levers.
[Illustration: FIG. 74.--FLAT BONE (Scapula).]
[Illustration: FIG. 75.--LONG BONE (Femur).]
[Illustration: FIG. 76.--SECTION OF BONE, MAGNIFIED.]
The bones consist of earthy matter, chiefly phosphate of lime, held
together by a sort of cartilage, and arranged in fine scales or plates
forming interstices or cells (fig. 76), these are large in the centre
of the bone so as to make it nearly (and in some instances quite)
hollow, and very small at the surface, so as to make it there nearly
solid; this arrangement is found to be the very best to secure strength
and lightness, together with a very slight degree of flexibility. The
general form of a long bone is that of a shaft, having an enlargement
at either extremity, the shaft is generally curved slightly so as to
give elasticity, and is more solid than the ends, which are expanded to
give size and firmness to the joints, and porous to keep them light;
the shaft is small and close in its texture, that there may be plenty
of room for the muscles which lie on and cover it. The skeleton then,
consists of bony cases which enclose the viscera, a series of levers
covered with, and moved by the muscles, and the whole forming a solid
framework to support the soft parts. All the various motions of the
body, from the winking of the eyelid and the wonderfully adjusted
motions of the eye itself--which are so accurate, that a certain
perceptible motion is required to look alternately at one side and
the other of a pin's head--to the most powerful stroke of the arm, are
performed by the contraction of the muscles. But there are several
actions which would at first appear to be produced by elongation
instead of contraction, such as the protrusion of the tongue, the
winking of the eyelids, and the closure of the lips; but the first of
these is produced by the contraction of a muscle which is attached at
one extremity to the under part of the root of the tongue, and at the
other to the inner part of the lower jaw, which, when it contracts,
draws the whole tongue forwards, causing a part of it to protrude;
the eyelids and lips are closed by circular muscles surrounding them,
which, by contraction, draw together those parts.
[Illustration: FIG. 77.--FIBRILS OF VOLUNTARY MUSCLE, MAGNIFIED.]
[Illustration: FIG. 78.--THE SAME, MORE HIGHLY MAGNIFIED.]
The muscles form the flesh of an animal, or that part which is of a red
colour, and which is called lean (in contra-distinction to fat), they
are composed of fibres, each fibre made up of a number of fibrils, and
the whole bound up together by means of a fine membrane, called areolar
tissue. Each of these fibrils consists of a number of cells pressed
closely together and having a peculiar bearded appearance (figs. 77,
78). It is by the sudden approximation and flattening of these cells
that the muscle is shortened during contraction, but the contraction
of each fibril is only for an instant, and then a relaxation and
elongation of the cells takes place, which is followed by a second
contraction, and so on. Now, the way in which a muscle keeps in a state
of permanent contraction is this: the various fibrils or strings of
cells relieve each other instead of all contracting and all relaxing
together, and in this way a part only of the fibrils are in a state
of contraction at any given time, while the others are relaxed, and
as one begins to relax another contracts, and so keeps up a state of
contraction in the muscle up to a certain point, when the contractions
become gradually more feeble, and finally cease altogether; the muscle
is then exhausted, but, if allowed to rest awhile, it again obtains its
contractile power. This peculiar contractile power is a physical one,
and exists for a short time after death, that is, until its perfect
structure is altered by the beginning of decomposition; and what is a
curious fact, the muscles of a dead body stimulated to contraction by
pricking or galvanism, will tire and again obtain their contractility
by rest, just as in the living body. The nature of the stimulus which
causes the muscles to contract during life is not known; but, whatever
it may be, it is conveyed from the spinal cord and brain, through the
medium of a set of nerves, called the "motor nerves," or nerves of
motion, to the muscles, to every fibre of which they are distributed.
There is, however, another set of nerves which have nothing to do
with motion, although exactly similar in appearance and generally
associated and bound up in the same sheath with them; these are the
nerves of sensation. They take their origin from every part possessed
of sensibility or feeling--more especially the skin--and convey every
impression of feeling to the brain. The muscles are not all under the
control of the will, for the muscles of the heart, bowels, &c. are
quite out of our control. Those which are subservient to our will are
called "voluntary" muscles, or the "muscles of animal life," while
those out of the control of the will, are the "involuntary" muscles,
or "muscles of organic life" (fig. 79). These last have a structure
different to the voluntary muscles, being composed of flattened fibres
containing granules and overlapping each other. The tendons are the
cord-like extremities of the muscles which connect them to the bones;
they are fibrous and slightly elastic, flexible, and exceedingly
strong; while moist they have a splendent appearance, somewhat like
mother-of-pearl.
The ligaments are the strong fibrous bands which connect the bones
together. Cartilages are substances of a white colour, smooth in
their texture, and not very flexible; they are connected to the
bones which they sometimes serve to prolong, and are themselves often
converted into bone in old people, by the deposition of earthy matter
within their structure, in fact, they may be considered as bone in an
undeveloped state; for, in the infant, many parts are cartilaginous,
which, in the adult, are bony; such as the ends of the long bones, the
bones of the nose, &c.
[Illustration: FIG. 79.--INVOLUNTARY MUSCULAR FIBRE.]
[Illustration: FIG. 80.--HEAD OF AN INFANT.]
[Illustration: FIG. 81.--HEAD OF AN ADULT.]
With respect to the development of the form of the human body, there
are two chief conditions which influence it, namely, age and sex. With
respect to age, the proportional magnitudes of the different parts,
early and late in life, vary very considerably. In the infant (fig.
80) the hand is by far the most completely developed (in size), next to
this the abdomen, then the chest and upper extremities, and, finally,
the lower extremities. In the adult (fig. 81), the largest measurement
is round the chest and shoulders, but in the infant it is round the
head; in the adult the lower extremities weigh one half of the whole
body, but in the infant not one quarter. The infantile face has many
peculiarities, so also has the face of old age (fig. 82). In the infant
the lower part of the face is but little developed, the lower jaw
is small, the chin scarcely at all prominent, and the distance from
the nose to the chin very short, owing to the absence of the teeth,
or (when formed) their smallness. The bones of the nose are scarcely
formed, and this organ has therefore no bridge, properly so called;
the nostrils are small, the lower part of the forehead small, smooth,
and rounded, and the arches of the eyebrows but little prominent. The
cheek-bones are small, and so are the bony arches which join them to
the temples; the cheeks are full of fat, and the angles of the jaws
rounded. In middle age the lower part of the forehead becomes more
fully developed, the bony edges which support the eyebrows project
and overhang the eyes, the bridge of the nose and the nostrils become
more fully formed, the space from the nose to the chin is greater,
the teeth cause the lips to be pushed more forward, the lower jaw is
larger, and the cheek-bones show more plainly. In old age the whole
upper part of the face becomes more marked, the nose and eyebrows still
more prominent, the cheeks hollow from absorption of the fat, the space
from the nose to the chin (as in infancy) shortens from loss of teeth,
but the chin, being more fully formed, projects as the jaw rises to
fill the space occupied by the teeth. The angles of the jaw are also
very sharp and square, the eyes sunk in the head, and the whole skin
of the face loosened and wrinkled from loss of substance beneath. With
respect to sex, in the Male the facial bones are more fully formed,
the shoulders broader and higher, the collar-bones longer and more
curved, the chest wider, the hips narrower, and the legs longer, and
every bone has its processes or markings more fully developed, and is
more contorted from the action of the muscles, which are larger and
more powerful than in the Female. In the Female (fig. 83) there is a
greater deposition of fat, and, in many other respects, a tendency to
a child-like conformation.
[Illustration: FIG. 82--HEAD OF AN OLD MAN.]
[Illustration: FIG. 83.--HEAD OF A FEMALE.]
The body is everywhere covered by a common integument called the skin,
beneath which is a layer of areolar and adipose tissue, which last has
its cells filled with fat, which during life is in a liquid or oily
state; this serves to protect the parts beneath both from cold and
violence, fills up the hollows and irregularities between the muscles,
and gives the body a more rounded and graceful appearance.
Man, in common with all the higher animals, is possessed of the five
"special senses," namely, sight, smell, hearing, touch, and taste, the
organs of which are the eyes, nose, ears, skin, and mouth; but these
are developed in very different degrees in different animals.
[Illustration: FIG. 84.--FRONT VIEW OF EYE.]
_Sight_ is the sense by which we take cognisance of those external
objects which either give out or reflect light. The eye (fig. 84) is
an optical instrument of great beauty and perfection, and by its help
an image of everything we look at is produced in miniature on the
expanded optic nerve called the "retina," as an image is produced in
the "camera," which instrument is made in imitation of the eye; this
image by some unknown power is perceived by the mind, and produces
the sense of vision. By the sense of sight we recognise all forms,
colours, and gradations of light and shade, and also (assisted by the
experience gained by the sense of touch) the qualities of surface, such
as roughness, smoothness, &c.; for instance, we know by touch that a
piece of glass is smooth, that a piece of velvet has a different kind
of smoothness, &c., and the mode in which these surfaces reflect the
light, teaches us to recognise them so that we could predict from touch
what appearance an object would have, or by the look how it would
feel. Our knowledge of the solidity of bodies is known to the sense of
sight by (unconsciously) looking at them with each eye alternately,
so as to see to a certain extent round them, or somewhat on either
side alternately. By this fact the principle of the stereoscope is
explained, the pictures looked at through it, consist of two views
of the same object, taken at points of sight a short distance apart
(corresponding to the distance between the eyes) and they give us, when
steadily looked at, the same result that real objects do when looked
at with each eye, alternately. It is a curious fact, but one which has
been clearly demonstrated by optical experiments, that the picture
represented on the "retina" is inverted, but from habit we refer things
to their natural position, and how naturally and easily this is done,
may be ascertained by holding the head down close to the floor, and
looking at objects through one's legs, in this position they are all
inverted; but we naturally make ourselves satisfied that they are still
as they were before, so that they really do not appear to be inverted.
The impression formed by objects upon the retina is not immediately
destroyed upon their removal, but remains for an instant permanent;
this gives rise to a great many curious phenomena, among which the
most familiar is the circle of light produced by the rapid evolution
of any luminous body, as the red-hot end of a stick. This is also
shown by a toy, called the "Thaumatrope," which consists of a piece of
card having a small wire attached to the upper part by which it may be
turned rapidly round by the thumb and finger. On one side of the card
is painted an object, such as a parrot, and on the other a cage; when
the card is turned round, first the bird and then the cage is presented
to the eye, but the image of the one has not left the eye before the
other is presented to it, and the result is the uniform appearance on
both sides of a parrot _in_ a cage.
The structure of the eyes in Man and the higher animals is very nearly
alike, so that the same description will serve for both, but those of
insects and the lower orders of animated beings are very different.
[Illustration: FIG. 85.--SECTION OF HUMAN EYE.
A. Sclerotic.
B. Choroid.
C. Retina.
D. Vitreous humour.
E. Aqueous humour.
F. Cornea.
G. Crystalline lens.
H. Pupil.
I. Optic nerve.
]
The eye consists of various humours of different densities enclosed
in membranes (fig. 85); the human eye is spherical for the posterior
four-fifths of its circumference, but the front part projects a little,
being formed of part of a smaller sphere. The globe of the eye, all
but this front part, is enclosed in a firm fibrous coat called the
"sclerotic," within which is a membrane full of blood-vessels called
the "choroid," this on its inner side is covered with a black substance
called the "black pigment," and within this (lining the ball) is the
nervous coat or retina, it is the optic nerve so expanded as to form
a lining to the membranes of the ball of the eye for the greater part
of its extent. The ball of the eye is filled with a transparent fluid,
somewhat glutinous, called the "vitreous humour;" stretched across the
front part of the ball of the eye is a membrane having a round hole in
its centre, called the "iris," coated (like the choroid) with black
pigment on its back surface; this membrane (the iris) is the coloured
part of the eye, and its transparency or opacity determines the colour
of the eye. The pupil is the hole in its centre, it looks black because
the black pigment which covers the inside of the ball of the eye (for
the retina is transparent) is seen through it; behind the iris and in
front of the vitreous humour, is the crystalline lens, it is just the
shape of a very thick lens, but is more convex behind than in front, it
is quite transparent, and of a density almost approaching to solidity.
The front fifth of the ball of the eye is covered in by a dense
transparent substance called the cornea, of the form of a watch-glass
and quite transparent, between this and the crystalline lens there is
a small space called the anterior chamber, filled with a clear watery
fluid called the aqueous humour. The eye is moved by six muscles, four
straight and two oblique, these turn it in every direction with the
greatest accuracy; the front of the eye is defended by the eyelids,
which by winking and being moistened by the tears, keep the eye always
moist and free from dust.
The eyes of insects and several other classes of animals are called
compound eyes, and the image they produce must resemble objects
depicted in mosaic, or made up of small spots of distinct colours; they
consist of hundreds of small tubes, radiating and forming part of a
sphere on each side of the head, each of these tubes admits the light
from objects at which they point. Some of the animals still lower in
the scale have simple spots of transparent membrane with an expansion
of optic nerve beneath them; in such creatures the power of vision is
probably limited to distinguishing light from darkness.
[Illustration: FIG. 86.--SECTION OF THE HUMAN EAR.
_a_, external opening; _b_, tympanum; _c_, small bones; _d_, Eustachian
tube; _e_, cochlea; _f_, semicircular canals.]
_Hearing._--Sound is conveyed to the mind by the vibration of air, and
this vibration is communicated to a membrane within the ear, called the
"tympanum;" this is in connection (by means of three minute bones) with
the expanded auditory nerve, which ramifies within the "vestibule,"
which is filled with a fluid, so that the vibrations of the air are
thus communicated to the nerve of hearing (fig. 86).