Part 4

The most remarkable part of the skeleton is the spinal column, commonly called the back-bone. It is made up of twenty-six bones, or spines, which are united together in a marvelous manner, combining strength and freedom of motion. Each spine has a central aperture which communicates with that of the adjoining spines, thus forming a long canal in which the spinal cord lies. This cord connects the brain with the various parts of the body. There is a soft cushion of cartilage between each spine, which adds much to the elasticity of the back-bone, protecting the brain from shocks. This protection is further accomplished by the curvature of the spine. These bones are not placed directly over each other, but are so arranged as to give three curves to the spinal column. Along the column there are openings, at each joint, through which the nerves come to supply fibers to the different organs of the body.

_The spine rests on the pelvis_, which is a large double bone, basin-shaped, that sustains the abdominal organs. The pelvis, in turn, rests on the thigh bones.

_The thigh_ bone, “femur,” is the largest single bone in the body; it is joined to the pelvis by a ball and socket joint, an arrangement which permits its motion in any direction. The femur is supported by the bones of the leg. These are two in number in each leg, the tibia and fibula. The former is much the larger, and the latter is often called the “splint bone.”

The bones of the arm corresponding to those of the leg are the humerus, the radius, and the ulna. The humerus is the bone of the upper arm, and is large and strong; it articulates with the body in so perfect a manner that the great variety of motions required to be performed is easily and gracefully accomplished. This bone is fastened by a ball and socket joint, but is not, like the thigh bone, firmly fixed to an immovable bone. It is attached to a broad bone called the scapula, or blade bone; this is fastened to the body by muscles which give it great freedom of motion. The bones of the fore arm are the radius and ulna: these are nearly of the same size; in this they differ from the leg bones.

_The wrist_, composed of eight bones, forms the support for the tendons, blood vessels, and nerves which pass to the hand. To these are attached the metacarpal bones which support the phalanges, or bones of the fingers. The arrangement of the bones of the foot is, in many respects, like that of the hand. However, the bones of the foot form an arch which acts like a spring when the weight of the body falls on it, thus helping to ward off shocks and jars.

_The skull_ is a large bony case in which the brain is lodged, and by which it is protected. It is composed of several pieces firmly united by a very irregular line of union. The attachments of the skull are the jaw bones, nasal bones, and the cheek bones.

_Joints_ have been provided wherever parts of the skeleton require motion; they are of several kinds, chief among which are the ball and socket, hinge, and flat joints. The hip has been mentioned as a perfect example of the ball and socket joint, while the knee presents an example of the hinge.

_Muscles_ are necessary to all motion, and are found everywhere throughout the body. They are the active agents, which, under the control of the nerve centers, do all the work necessary to carrying on the functions of the organs. They are endowed with a remarkable property called contraction. How this is accomplished is not fully understood, but when stimulated by nerve force or electricity they shorten and widen. This brings their ends nearer together; also the parts to which they are attached. They are always attached to movable parts; their attachment is a tendon at one end, and a fan-like distribution of their fibers at the other. Tendons are inelastic fibrous tissue, very strong, and consequently much smaller than the muscle. They are to muscles what tugs are to horses. Muscles are either flexors or extensors; the former bend the joints, the latter straighten them.

_The skin_ forms an exterior covering for the body, and is employed for other and very important functions. Its appendages are the hair and nails. Some of the uses of the skin are these: It is highly sensitive and capable of distinguishing various sensations; it has the property of excreting, of secreting, and of absorbing. It is an organized texture containing blood vessels, glands and nerves. It is composed of several layers; the outside, called the epidermis, is not supplied with blood vessels, and is produced by the under layers.

_The glands_ of the skin are first, those which secrete the perspiration. This is poured out to keep the temperature of the body even, also to rid the circulation of many injurious substances. Then there are glands which secrete an oily matter which aids in preserving the softness and pliability of the skin. These glands are called sebaceous glands. Hair is said to be an appendage of the skin because its texture is essentially similar to that of the cuticle. Nails, also, are but modifications of the skin. The fact that the epidermis is being constantly cast off and renewed, and that matter is both secreted and excreted continually, renders frequent washing of the skin necessary to health.

_Digestion_—In animals the arrangements which exist for converting aliment into blood are more or less complicated according to the requirements of each class; and this conversion is called assimilation, a term which includes digestion and those changes which take place in the blood and tissues, by which new material is added to them.

The preparation of the food for assimilation by the tissues is accomplished in a long tube called the alimentary canal. This canal is made up of various parts having different functions and different construction. These parts we will briefly describe. They are the mouth, pharynx, æsophagus, stomach, small and large intestine.

As solid food requires to be broken up or ground before it passes into the stomach, the mouth is provided with teeth firmly implanted in the jaws, while the lower jaw is moved by strong muscles in two directions, one vertical, the other lateral. Man is supplied with two sets of teeth; the first adapted to the jaws of childhood; the second larger, which replace the former, are designed to last through life. The rudiments of each set are found in the jaws before birth. During the grinding or mastication of the food it is moistened and softened by a fluid called saliva. This also acts chemically upon it, changing the starch into sugar. The food is carried from the mouth to the stomach in a long tube called the æsophagus, by means of the muscular contraction of this tube.

_The stomach_ is a flask-shaped organ consisting of a double wall of tissue, the outer one being muscular, the inner one vascular. This latter membrane has a large supply of blood vessels, which convey the blood out of which the gastric juice is manufactured and secreted by the little glands of this membrane. The gastric juice is a fluid which contains an active ingredient called pepsin. This, aided by the acid which this fluid contains, effects a remarkable change on the albumen of the food, making it a liquid. From the stomach the food passes into the small intestine, where it receives from a small tube the pancreatic juice which changes the fat into an emulsion.

_The intestine_ is a tube, about twenty-five feet in length, which, like the stomach, has a double wall. Its inner coat contains multitudes of little projections called “villi.” These contain blood vessels which absorb and carry off the liquified food. It also secretes a fluid called intestinal juice, which acts upon the unchanged starch, making it into sugar. Its muscular wall by a continuous contraction produces a motion known as the “peristaltic motion,” which carries the food onward in its course. The intestine also receives the bile, a fluid produced by the liver.

_The liver_ is the largest gland in the body. It receives the portal vein which conveys the blood from the intestines. This vein, after dividing and sub-dividing, thus bringing blood into communication with all parts of this organ, is again collected into a main trunk which passes on toward the heart. During its passage through the liver the bile is eliminated from the blood by the little cells of which this gland is composed. From the liver the bile is carried toward the intestine, into which it is poured to assist in digesting the food, and to be itself changed.

Besides the little blood vessels in the _villi_ of the intestines there is another set of vessels called the lacteals, which aid in taking up the digested food and pouring it into the circulation; also, throughout the body a set of similar vessels collect the waste material and pour it into the great veins, returning to the heart, in order that it may be renovated or cast off; these are the lymphatics.

_The kidneys_ are great excretory organs, and are similar in shape to those of a sheep, but are somewhat larger. They are glands, and excrete urea, as well as other salts and waste materials, all of which are highly poisonous if not removed from the blood.

_Blood_ is the life-giving fluid of the body: it is the source from which all tissues are built, and it is the workman that carries the waste material away from the tissues. In order to accomplish its work it must circulate, and this requires a separate set of organs. First, the impure blood must be carried back from the different parts of the body; then it must be distributed again. It must also be made to flow onward in a continuous current. Blood is a viscid fluid, of a red color, containing over seventy per cent. water, with solid matter. Its color differs on each side of the heart. When it returns from the body it is blue, but when it leaves it is red. Under the microscope it is seen to contain minute globules, or disk-like cells; to these the blood owes its color. It possesses the remarkable property of spontaneous coagulation when drawn from the veins. It is forced on by the heart.

_The heart_ is a muscle and consists of four cavities; two called auricles having weak walls, and two ventricles with strong muscular walls. The blood returning from the body is poured into the right auricle, thence into the right ventricle; from this cavity it is forced through the lungs and returns again to the heart, being poured into the left auricle, which empties into the left ventricle. This ventricle forces the blood throughout the body. The blood received by the heart from the body is impure, and is sent to the lungs, where it gives up part of its impurities and receives oxygen from the air.

_Arteries_ are those vessels that distribute the blood, while the veins collect it and return it to the heart, thus all streams of blood leaving the heart are conveyed in arteries, and those pouring into it are carried in veins.

_The lungs_ are the organs that purify the blood, and in order that this be thoroughly done, the blood is distributed throughout their substance in minute capillary vessels. The lungs themselves are vascular; being made up of a multitude of air cells, their surface is greatly increased; hence their power of absorption. The diaphragm is a muscular partition lying below the lungs. It is dome-shaped, and when its fibers are shortened it enlarges the cavity in which the lungs are situated. This creates a partial vacuum, causing the air to rush into the lungs. The blood absorbs the oxygen from the air and gives up carbonic acid gas. When the muscles of the diaphragm are relaxed the elastic force of the air cells in the lungs expels the remaining gases from the lungs. The diaphragm is assisted by the action of muscles situated between the ribs; these lift the ribs and enlarge the cavity of the thorax. The lungs also act as a reservoir for the air used in the production of vocal sounds. They communicate with the atmosphere by means of a tube called the trachea; this terminates in the pharynx, with which the nostrils also communicate, thus completing a passage to the outside air.

_The voice_ is produced by the modifications which the teeth, tongue, lips and throat make upon the sound produced by the vocal cords. The vocal cords are stretched across the upper end of the trachea, which is called the larynx. The air from the lungs is forced past them, setting them in vibration, thus producing sound.

_The nervous system_ consists first of all of the brain. This is composed of nervous matter and constitutes the mass contained in the skull. It is divided into three parts: the cerebrum, the cerebellum, and the medulla oblongata. These three parts seem to preside over different functions. Thus, the cerebrum is the seat of the faculties of the mind, while the cerebellum presides over the muscular actions. The brain is connected with distant parts of the body by means of fibers which are distributed to all parts. These fibers are of two kinds, one set carrying the impressions to the brain, the other carrying the stimulus from the brain to the organs. The former are called sensitive, the latter motor nerves. A deep fissure separates the brain into two lateral halves, and these parts are connected with opposite sides of the body. Besides these nerves, which originate in the brain and pass through the spinal cord, there are twelve pairs that pass directly through the skull to the organs which they supply. These are called cranial nerves, and are distributed to the eyes, the nose, the ears, the larynx, the lungs, the face, stomach, etc. Ten of these pairs of nerves originate in the medulla oblongata. Of the functions presided over by these nerves may be mentioned those performed by the tongue, (taste), eyes, ears, and nose.

Many of these nerves are not sensitive, in the ordinary use of the word. Thus, the retina of the eye is the expansion of the optic nerve, and, while it is sensitive to light, it is not to ordinary impressions, such as material contact. Also, the nerve of the ear is only sensitive to the vibrations of fluids. We see by light reflected from objects. This light passes through a set of lenses, and by means of these an image is formed on the retina, which impression is carried to the brain. Just how all this is accomplished is not known. The nerve of the ear floats in a fluid called lymph. This fluid receives the vibrations of bodies through the air, through the membranes and chain of bones, and thus the nerves receive and transmit them to the brain, which act constitutes hearing.

Volumes could not tell all that one single fiber of muscle contains that is instructive, much less the entire functions, constructions, and mysteries of a single organ of special sense. And to perform all the allotted functions every part must be in the best repair. This constitutes health. Health is maintained by cleanliness, by repose, by muscular activity, by moderate eating, by plenty of fresh air, by a contented disposition, and a clear and active mind. Watch over your body with a jealous care, for all your future depends upon its good condition.

SUNDAY READINGS.

SELECTED BY THE REV. J. H. VINCENT, D.D.

[_April 1._]

THE LAW OF THE HOUSEHOLD.

By E. A. WASHBURN, D.D.

“Honor thy father and thy mother; that thy days may be long in the land which the Lord thy God giveth thee.”—Exod. xx: 12.

We open this second division of the Law with the duties of man to man; and at its head stands the commandment of the household. I must repeat here the remark of eminent scholars, that each of the original tables probably contained five statutes; and thus the maxim we now consider was directly joined with the four concerning the worship of God. Such a view gives us indeed a new insight into the Hebrew religion, which linked the first of social truths with a divine faith; it is the anticipation of his Gospel, who has taught us that the love of parent and children is the type of our holier bond in the family of Christ. But there is a yet further thought in the words of this “commandment with promise.” That “thy days maybe long in the land.” Those earlier commandments tower above us like the lonely heights, where Moses communed with God; but as we read this sentence, we see rise on the eyes of the lawgiver the landscape of far Judea, with its laughing fields, the voice of children and the home of calm old age. These words suggest the whole line of our reasoning on this subject. Filial reverence is the fountain of all affections, all duties; it flows like the river of Eden, parted into its branching heads, through every channel of human life.

It is then the family, as the institution which God has implanted in our nature, and Christianity has hallowed, that we are to consider. I know indeed no richer study than thus to trace its growth. I have no theories to offer you. It is the simplest of facts. There has been no more favorite field for our philosophers than that of the origin of human government. Some have fancied that men met together in formal compact; others have held the state of nature that of a pack of wolves, at last brought together by self-interest to choose some kingly wolf, who could keep the peace; and we have to-day our sages, so enamored of their researches into comparative anatomy, that they can pass by all the nobler facts of social history, and find the primitive man in some anthropoid ape. Yet as the grandest laws of God are revealed in the nearest example, we learn more than volumes of such theory in the life of our own households. Government began with the family. It is no artificial thing. It was not imposed by force. There is no state of nature that goes before it; but as all our discoveries in organic life lead to the primary cell, so all social formations are only the enlargement of this little human embryo. We need no other truth than that he, who gave us this moral being, made us to dwell in mutual dependence; and thus the germ of all authority lies in the relation of parent and child, in the care it calls forth, in the weakness of infancy, and the natural reverence that springs from the heart. Open the Book of the Genesis; you see the patriarch Abraham dwelling in the tent with his children; you see this household passing into tribes, linked in a bond of brotherhood, reverencing the father of them all, who is priest and head; and you trace further on a Mosaic commonwealth. History repeats the same early chapter in the Arab of the desert to-day, or in the beginnings of ancient Rome. “Society in primitive times,” it is said by one of the wisest of English jurists, in his work on Ancient Law, “was not a collection of individuals; it was an aggregation of families.” Among all early peoples the law of the household is thus supreme; it embraces all duties, and reaches to the nicest detail of courtesy. The oldest laws of China are as rich in their family wisdom as any in the world. Filial reverence was the corner-stone of the state. I well remember with what surprise I saw the son of a venerable Parsee, himself a man of fifty, wait behind his father’s chair during a long interview; it was a vestige of the stately manners of the East, strangely contrasting with our civilized rudeness. But if we will find the finest examples in the past, we must turn to those scenes in the Old Testament, where the aged patriarch lays his hands on his eldest born in token of his birth-right, or the twelve gather reverently about the bed of the dying Jacob to receive his blessing. In this household life, interwoven with all their social habits, the heart of the Hebrew was nursed; and in many a quiet home, like that of Nazareth, there grew the blossoming graces of childhood, that made this history so pure amidst all its decays.

But we must pass from this earlier view to the new life of Christianity, if we would know its nobler influence. Many pure affections and virtues grew without doubt in a heathen civilization. But the family authority was almost a despotism; the father had power of life and death over the child, and woman was little more than a slave. The one great feature of all social progress, we are told by the jurist already cited, has been the recognition of the rights of the person, instead of absolute family dependence. Here it was that the religion of the Gospel had its living power, and I ask you to study this wonderful fact in its early history. As we look back on the state of society at that time, we are struck everywhere with the decay of those fair examples of chastity, of maternal virtue, of household strength which bloomed in the old Roman commonwealth. Family life had withered, because it had not in its ancient pagan form those elements which could preserve its influence amidst the shameless sensuality of the world. The public talk of the forum, the theater, the games, the busy out-of-door existence, such as you see to-day in Southern Europe, were everything; nor was there a purer tide flowing into the great city, as from the country homes of England and America, to cleanse and freshen it. Religion was a brilliant temple pageantry. Thus, as in all pagan lands, you have the same striking facts; the degradation of woman and the degradation of man with it. This it was that the religion of Christ changed. It taught, as its first truth, that God was our Father, and all men one brotherhood in Christ. What a revelation was this beyond all that the pagan mind had known! The paternal power was no longer a despotism to the believer; the father knew that he had a Father in heaven, and that his child was no serf, but the household tie was a type of the holier family of God. Read that clear utterance of the household law in St. Paul: “Children, obey your parents in the Lord; fathers, provoke not your children to wrath.” The Gospel cherished above all else the family authority; yet it hallowed, sweetened, enlarged it. It nursed the virtues of the household. It made woman the companion of the heart and home; it hallowed marriage; it taught the love of Christ and the brethren, contentment, industry, frugality, sacrifice, and charity to the poor. What picture so fair as in the letters of that time of its fresh, healthful life; that “church in the house,” breathing the soul of the early religion? The kingdom came without observation, without noise; and a new home-born, home-bred society grew in the midst of the dying civilization.

[_April 8._]

THE LAW OF THE HOUSEHOLD.