Part 20

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.

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.

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.

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.

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.

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.

_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.

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.

_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).