CHAPTER VIII

THE NERVOUS SYSTEM

=Review Questions introducing this Subject.=--What is a cell? What are the five supporting tissues? What are the two master tissues? Why are they so called? What kind of cells have many branches? Does the food ever come in contact with the salivary glands? When you look at a basket of apples, the sight “makes your mouth water.” Is there a connection between the eye and the mouth? What two tissues enable the skin to blanch and to blush? Do the different organs share the blood in the same proportions at all times? How can this proportion be changed? How is the brain protected from injury? How is the spinal cord protected? Is the hole for the spinal cord through the main body of the vertebra, or behind the main body?

=Harmonious Activity.=--Strike suddenly at the eye of another, and the lids fall to protect it, and the hands rise to ward off the blow. If a grain of dust gets into the eye, the tear glands form tears to wash it out. If you touch the hand unexpectedly to a hot iron, the muscles of the arm jerk the hand away. If the foot of a sleeping person is tickled, the muscles of the leg pull it away. Many muscles coöperate in the act of running. If the human being were merely an assemblage of working organs, the organs might act independently, and there would be such confusion that the body would be powerless, and life could not be maintained. The nervous system enables the organs to work together for the common good. Why does an ameba not need a nervous system?

=The Need of Nerve Centers as well as Nerves.=--If there were no central office in a telephone system of one thousand subscribers, then every subscriber, in order to communicate with every other subscriber, would need one thousand wires running into his house; all together, there would have to be several hundred thousand (to be exact, 499,500) wires. With a central office only one thousand are needed. As a telephone system has central offices, so the nervous system has nerve centers. Nerve centers contain nerve cells. Although there are some subordinate nerve centers in the spinal cord, the greatest collection of nerve centers in our bodies is in the skull, and is called the _brain_. Fishes were the lowest animals studied in animal biology found to possess a true brain.

The nervous system, unlike a telephone system, has other duties besides allowing _communication_. It enables us to _think_, and, after reflection, to _will_ and to _act_ by controlling the various organs.

[Illustration: FIG. 103.--Showing a NEURON, _A_, or nerve cell with all its parts--dendrites, cell body, and axon; _B_, a portion of a white fiber highly magnified. (Jegi.)]

=The Units of which the Nervous System is Constructed.=--A nerve cell with all its branches, or fibers, is called a _neuron_ (see Fig. 103); some neuron branches are several feet long. Neurons are the units that compose the nervous system. The living substance in cells is called _protoplasm_. The protoplasm in nerve cells possesses the most marvelous and varied powers of any known substance, for the nerve cells are the seat of the mind.

[Illustration: FIG. 104.--LARGE NERVE TRUNK, such as supplies the muscles. Cross-section (magnified 6 diameters), showing bundles of nerve fibers. (Peabody.)]

=Nerve Cells and Fibers.=--The many branches of nerve cells make them the most remarkable of all cells for irregularity in shape. Since _the protoplasm of the cell continues into the fibers_, it is plainly wrong to consider the nerve cell as something apart from its fibers. It is not a complete cell without them. A cell usually has many short branches called _dendrons_ or _dendrites_ (see Fig. 103) for communicating with near-by cells, and one long branch called an _axōn_ (Fig. 103) for communicating with distant parts. The axons form the fibers that go to the skin, muscles, and other organs.

=A Nerve.=--These long branches, or axons, of nerve cells go all over the body and are often bound together into visible cords called _nerves_, or nerve trunks (Fig. 104).

[Illustration: FIG. 105.--_c_, a white fiber with its fatty sheath (dark); _d_, two gray fibers (without sheath).]

=White and Gray Fibers= (Fig. 105).--Some fibers have a _fatty covering_ surrounding the _thread of protoplasm_; they are white and glistening, and are called _white fibers_. Others are without this fatty covering, and are called _gray fibers_. Both kinds of fibers have _connective tissue_ on the outside to strengthen them. If we let a lead pencil represent a white fiber, the lead corresponds to the axis of protoplasm; the wood corresponds to the white, shiny fat that surrounds it; and the varnish corresponds to connective tissue on the surface of the fiber. A number of white fibers together makes a white mass that is called _white matter_. The axis of a white fiber, of course, is not white. A mass of cells or of gray fibers is called _gray matter_. The oxidation of the gray matter, or protoplasm, in neurons gives rise to nerve energy.

=Feeling Cells and Working Cells.=--Nerve cells are divided into two classes: _sensory cells_, which feel or receive impressions; and _motor cells_, which send out impressions to the working organs. Those fibers which carry impressions to the receiving cells are called _sensory fibers_; those which carry impulses from the cells to the working organs are called _motor fibers_.

=Ganglia and Nerve Centers.=--Nerve cells are not scattered uniformly in nervous tissue, but are gathered into groups. A group of nerve cells is called a _ganglion_ (Fig. 106). One or more ganglia having a single function, such as to control the muscles of breathing, form what is called a _nerve center_. The brain consists of a number of nerve centers with their connecting fibers.

[Illustration: FIG. 106.--A GANGLION.]

[Illustration: FIG. 107.--CROSS-SECTION OF SPINAL CORD, showing area of gray matter (dark).]

=Gross Structure of the Spinal Cord.=--The nerve fibers from nearly all over the body lead to cells situated in a large cord in the spinal column called the _spinal cord_. The spinal cord is _separated by a deep fissure almost into halves_ (Fig. 107). The cells are situated in the central portion of each half, and the _two masses of gray matter_ thus formed are connected by a narrow isthmus of gray matter. The outer part of the cord consists chiefly of white fibers. The _white matter is thus on the outside of the cord_ (Fig. 107). The brain, unlike the cord, has the gray matter on the outside and the white matter on the inside. For microscopic study of the spinal cord, see Fig. 108.

=The Work of the Spinal Cord.=--There are two functions of the cord: reflex action and transmission of impulses from the body to the brain. Reflex action is action that takes place without the aid of the will.

[Illustration: FIG. 108.--SECTION OF SPINAL CORD, showing nerve cells (large black spots) with their branches (black dots and lines). Five bundles of nerve fibers are shown near upper margin. (Peabody.)]

=Reflex action= never begins in the cord, but at the outer end of a sensory fiber, usually located in the _skin_. The impression goes to the cord along a _sensory fiber_. It is received in a _sensory cell_ and transferred by dendrons to a _motor cell_ which sends back an impulse along a _motor fiber_ to a _muscle_; the muscle contracts and the action is complete. At least two nerve cells are necessary for reflex action. The actions of the lowest animals are almost entirely reflex.

=Reflex Action, Consciousness, and Will.=--Usually not all of the force of the impulse is transferred to the motor cell. The sensory cell by means of another of its many branches may _transfer part of the impulse to a cell which sends it to the brain_. Hence a reflex act is not necessarily an unconscious one. If you unintentionally touch the hand to a hot stove pipe, you may be conscious of the pain and the involuntary jerking away of the hand at the same time.

=Reflex Action and the Will.=--The will may _inhibit_, or prevent, an expected reflex act. Yet many reflex acts occur in spite of the effort of the will to prevent them. One cannot always keep from closing the eyes before a threatened blow even if from the other side of a plate glass window, and it is known there is no danger. Sneezing is a reflex act and cannot always be prevented. The forming of saliva and other secretions are reflex acts. _Reflex acts are quicker than voluntary acts._ An eighth of a second is about the time required for a person to press an electric button after seeing a signal; a reflex act may occur in a shorter time.

[Illustration: FIG. 109.--BRAIN AND SPINAL CORD.]

=The Brain consists of Three Chief Parts.=--(1) There is an enlargement at the top of the spinal cord called the _medulla_, or the medulla oblongata. It may be regarded as the part of the spinal cord within the skull (see Figs. 109, 110, 114). (2) Above the medulla is the _cerebellum_, or little brain. (3) The _cerebrum_, or large brain, fills all the skull except the small part occupied by the medulla and cerebellum. The cerebrum covers the cerebellum. (Fig. 110.) Is this true of the monkey’s brain? (See Fig. 113.)

=The work of the medulla= is chiefly to control the vital functions (see Figs. 110, 114). Here are located the centers for regulating the _breathing_, the _heart beat_, the _size of the blood vessels_ (thus regulating nutrition), and also the less important centers that control _swallowing_, _secretion of saliva_, and _vomiting_. The center for breathing is sometimes called the _vital knot_, because although the cerebrum and cerebellum may be removed from an animal without causing immediate death, the slightest injury to the vital knot kills the animal at once. In cases of hanging, death is caused by injury to this center.

[Illustration: FIG. 110.--THE BRAIN (cerebrum, cerebellum, medulla).]

[Illustration: FIG. 111.--ASSOCIATION FIBERS, connecting cells within the cerebrum. (Jegi.)]

=Automatic Action.=--The center called the vital knot is said to regulate the breathing automatically, not reflexly. Reflex acts start in the skin; _automatic acts start in the interior of the body_. _The condition of the blood regulates the breathing_ automatically during sleep, and partly regulates it during waking. If too much carbon dioxid accumulates in the blood this excites the vital knot, which sends out stronger impulses to the respiratory muscles. Deeper breathing follows, which purifies the blood, and the breathing is then shallow or slow until carbon dioxid accumulates again.

=The Four Kinds of Nerve Action and the Centers that control them.=--The _cord_ controls chiefly _reflex_ action; the _medulla_ controls chiefly _automatic_ action; the _cerebellum_ controls chiefly _coördinate_, or harmonizing, action; the _cerebrum_ controls the purely _voluntary_ acts, for it is the seat of _consciousness_ and _thought_. The medulla, like the cord, has the gray matter on the inside (Fig. 109).

[Illustration: FIG. 112.--SENSORY AND MOTOR FIBERS. (Jegi.)]

=Structure of the Cerebellum.=--The cerebellum, like the cerebrum, has the gray matter or cells on the outside. The gray matter is folded into furrows that are not nearly so winding as the folds in the cerebrum (see Fig. 115). The fibers going to the surface cells have a branched arrangement called the _arbor vitæ_, or tree of life, which is shown where the cerebellum is cut. The cerebellum, like the cerebrum, is deeply cleft and thus divided into halves, called _hemispheres_, connected by a band of white matter.

[Illustration: FIG. 113.--BRAIN OF A MONKEY. Numerals show location of motor centers. (See Fig. 115.)]

[Illustration: FIG. 114.--THE LOBES OF THE RIGHT SIDE OF BRAIN and their functions. (Jegi.)

The speech center is true only for left-handed persons. Medulla is marked “Bulb.”]

=The work of the cerebellum= is to aid the cerebrum in controlling the muscles. _It coördinates the muscular movements_; that is, it makes the muscles act at the right time and with due force in complex acts, such as standing, walking, talking. A man could strike just as hard without the action of the cerebellum, but he would not be likely to hit what he aimed at. A drunken man staggers and fails to control the muscles in walking because the alcohol has caused the blood to collect and congest around the cerebellum and press upon it. One whose cerebellum has been injured by accident staggers like a drunken man.

[Illustration: FIG. 115.--MOTOR AND SENSORY AREAS OF LEFT HEMISPHERE. Speech center marked “Lips.”

In what region are the motor centers? The sensory centers?]

=Coverings of the Brain.=--Lining the skull and covering the cerebrum are found _two membranes_ which inclose a lymph-like fluid. Thus a kind of _water bed_ is made which surrounds the soft and delicate cerebrum and protects it from jars. A membraneous net, or meshwork, of blood vessels covers the cerebrum and plentifully supplies it with blood.

=Structure of the Cerebrum.=--The gray matter, or cell mass of the cerebrum, forms a surface layer, called the _cortex_ (“bark”), about one eighth of an inch thick. This _gray layer is deeply folded_, the folds, or _convolutions_, being separated by deep furrows, some of them an inch deep (see Fig. 110). Thus the area of the surface layer is increased to several times what it would be if smooth. Intelligence increases with increase in the number and depth of the convolutions. The greater part of the cerebrum is white matter. This consists largely of associational _fibers_ (Fig. 111) _which connect the cells in the gray matter with each other_ and with important interior ganglia at the base of the cerebrum (Fig. 112). These basal ganglia are the largest parts of the brains of the lower vertebrates (Animal Biology, Figs. 222, 259). Why do these animals not need large cerebrums? The human cerebrum comprises nearly seven eighths of the weight of the brain. A deep fissure divides it into the right and left cerebral hemispheres. A band of white matter connects the hemispheres.

=Functions of the Cerebrum.=--The cerebrum is the seat of _consciousness_ and thought, and of all activity controlled by the _will_. It also _directs the work of the lower nerve centers_ in the spinal cord, medulla, and cerebellum.

It receives sensory messages from all parts of the skin and through the special senses. It sends out motor messages to all the voluntary muscles, and more indirectly to the involuntary muscles. The cerebral fibers are of three kinds: _sensory_, _associational_ (connecting cells in cerebrum), and _motor_ (Figs. 111, 112). It is estimated that the cerebrum alone contains 9,200,000,000 cells.

=Spinal and Cranial Nerves.=--The nerves from the spinal cord go out through notches between the vertebræ. Since there are _thirty-one pairs_ of _spinal nerves_ (Fig. 109) and only twenty-four vertebræ, some of the nerves go out through holes in the sacrum. The _cranial nerves_ (to eyes, ears, tongue, nose, face, etc.) leave the brain through holes in the cranium, or skull. There are _twelve pairs_ of them.

=Relation of the Cerebrum to the Lower Centers.=--As already stated, nerve activities are of four kinds,--reflex, automatic, coördinate, and voluntary. A manufactory has more complex work than a shop. A man with a shop may enlarge it into a factory and leave trained assistants in charge of the different shops, keeping only the general management for himself. If he should cease to control his assistants entirely, the work of the factory would soon be in disorder. If the manager should try to direct everything, he would become exhausted. So the cerebrum, the seat of the will and the reason, leaves the reflex centers in the spinal cord, medulla, and cerebellum to do most of the work. If the mind wishes the hand to move and grasp the hand of a friend, the motor center in the cerebrum sends a message to the cerebellum; and if the cerebellum has been well trained, the act is accurately performed.

=A less imperfect wisdom than that of the mind= is in the lower nerve centers. The reason and will control the lower centers through the cerebrum, but the control is very limited. It is well that this is so, not only for the relief of the cerebrum, but for the safety of the body. Can you change the rate of the heart beat by the exercise of the will? Can you blush at will, or prevent the flushing of the capillaries when you are embarrassed, or when you go close to a hot fire? It is impossible for a person to commit suicide by holding the breath. What change in the blood would soon force a breath to be taken? Repeat the two examples of reflex action triumphing over the will which have already been given. We shall next take up a system of nerves almost independent of the will.

=The ganglionic or sympathetic= portion of the nervous system controls the viscera (_vis′sē-ra_), or internal organs, _e.g._ peristalsis of food tube, tone of arteries. The nerves that go to the viscera branch off from the spinal nerves not far from the spinal column, and enter a row of ganglia on each side of the spine (see Fig. 115). Each ganglion is connected by nerves with the one above and below it, so that they appear like two knotted cords suspended one on each side of the spinal column and tied together below; for both chains of ganglia end in the same ganglion in the pelvis. Some of the fibers from the spinal cord pass through these ganglia on their way to the viscera, losing their white sheaths in the ganglia and emerging as gray fibers. The spinal cord and brain with the fibers which do not pass through the double chain of ganglia are called the _cerebro-spinal system_. The double chain of ganglia and the fibers which go through them are called the _ganglionic_ or _sympathetic_ system.

[Illustration: FIG. 116.--DIAGRAM OF SYMPATHETIC SYSTEM showing double chain of ganglia; also plexus at heart and solar plexus.]

=Why these Nerves are called the Sympathetic System.=--These nerves, after leaving the double chain of ganglia, form many intricate networks of ganglia and fibers. Each network is called a _plexus_ (Fig. 116). The largest of the plexuses is just back of the stomach, and is called the _solar plexus_. A blow upon the stomach may paralyze this plexus and cause sudden death. _The plexuses and fibers connect the viscera so perfectly that one organ cannot suffer without the others changing their activity, or sympathizing with it._ An overloaded stomach causes the heart to beat faster and send it more blood; a loss of appetite usually accompanies illness and allows the stomach to rest. This sympathy is necessary, for if one organ is diseased, the others do not continue to work and tax the strength of the ailing organ.

=How the Sympathetic and Cerebro-spinal Nerves Differ.=--The ganglionic nerves (1) contain mostly _gray fibers_; (2) pass _through ganglia_ after leaving the spinal cord; (3) control the _unconscious_ activities of the body; (4) pass to organs which contain slow-acting _involuntary muscles_, not to sense organs and quick-acting voluntary muscles; (5) transmit impulses _slowly_ (about 20 ft. instead of 100 ft. per second). Crawfish and insects have hardly more than the ganglionic system of nerves (Animal Biology, Figs. 92, 132, 197).

=Examples of the Supervisory Functions of the Sympathetic System.=--Regulation of the heart beat and of the size of the blood vessels; secretion of sweat glands; contraction of pupils of eyes in a bright light; peristalsis.

=Examples of Sympathetic Nerve Impulses reaching Consciousness.=--Pain in colic and cramps; “heartburn” (pain in stomach from indigestion); backache (from nerves in organs prolapsed by tight clothing pulling upon their attachments at spine); hunger; thirst.

=The Mind and Health.=--A contented or peaceful mind is indispensable to soundest health. Worry causes difficult breathing with bated breath. Happiness brings full, easy breathing. Biological study of physiology shows the futility of making health a care or anxiety, and teaches “no meddling” with the body, whether by stimulating it, drugging it, deforming it, overheating it, half smothering it in close rooms, cultivating artificial instincts, etc. If the body degenerates through wrong living, and disease ensues, a new way of living is needed, not some quick and wonderful remedy. The new life will renew the body and nothing else can.

HYGIENE OF THE NERVOUS SYSTEM

=Necessity of Food, Fresh Air, and Rest for Sound Nerves.=--The health of the nerves depends upon a free supply of pure, nutritious blood. Nearly one fifth of the blood goes to the brain. It is clear that the brain cannot give out energy until it has first received it; the blood supplies energy to the brain. The blood in turn receives the nourishment from food and pure air. A rested cell is full of nourishment; a tired cell is shriveled (see Fig. 117).

[Illustration: FIG. 117.--EFFECTS OF FATIGUE ON NERVE CELLS.

_A_, resting cell, _B_, fatigued cell, with its body and nucleus shrunken.]

=Sleep.=--During waking hours energy is used up faster than it is stored in the cells, and protoplasm is oxidized faster than the cells can replace it. During sleep the opposite is true; repair is more rapid than waste. During sleep the muscles are strengthened, the breathing is less, the heart beats more slowly, less heat is produced, digestion is slower, less blood goes to the brain. Why is it necessary to be more warmly protected by clothing or bed covering when asleep than when awake? Above all, the nervous system has an opportunity to recuperate from the constant activity of waking hours. The eye and the ear are rested by darkness and silence. Sleep caused by morphine or other drug is not normal sleep and brings little refreshment.

=Practical Suggestions.=--Sleep is deepest during the second hour after going to sleep, and a greater shock is given to the nervous system by waking a sleeper during that hour than at another time. An alarm clock is a very unhealthful device. One who cannot trust to nature even to awaken has great presumption. If one does not rise promptly upon waking naturally, the instinct to awake when enough sleep has been taken will be lost, and the habit of sleeping too much will be formed, and the brain, like the muscles, will become weak from inactivity. Infants sleep most of the time, and it is injurious to them to be waked. Adults usually require about eight hours of sleep. There is a risk in going to sleep in a warm room, for the bed covering which is comfortable then may not be enough to prevent taking cold when the fire goes out. Sleep usually comes more promptly to one who goes to bed at the same hour each night. The muscles are relaxed in sleep, and relaxing them perfectly upon lying down and breathing slowly, tends to bring sleep. One who is sleepless usually finds that he is breathing fast and is holding the head stiff on the shoulders, the teeth clenched, and the muscles contracted, even though he is lying down. Excitement and worry during the day, but especially just before retiring, tend to produce sleeplessness. One who overworks his mind by too great attention to business is inviting ruin. A student who loses sleep while preparing for an examination will probably fail. Rested brain cells and pure blood are needed for good work.

=Rules for Preventing Sleepiness.=--(1) Do not sit close to stove or especially a fireplace or in very warm room, and do not wear very warm clothing in the house. (2) Let in fresh air freely. (3) Do not sit in rocking chair nor with chest flattened. (4) Make the last meal a very light one.

=Habits.=--Our habits of doing and thinking and feeling really constitute our characters. This shows the importance of right habits. By gradually changing our habits we can strengthen our characters and form them somewhat as we wish. When a muscle contracts in a certain way, this act makes it easier for the muscle to contract in that way the next time; thus great muscular strength may be developed. _When a nerve cell acts, the circulation around the cell is increased, the fibers develop by use, and the act is easier the next time._ We cannot entirely get rid of our habits, because we cannot get rid of our brains.

=Healthy fatigue= is caused by the accumulation of waste products resulting from the oxidation of substances in nerve, muscle, and gland cells. The presence of waste in the tissues affects the nerves. We are rested and strong when these wastes are removed and the tissues are supplied with fresh food and oxygen. Work causes the accumulation of _carbon dioxid, which is nature’s narcotic_.[9] The drowsy feeling that ensues is more pleasant than the drowsy feeling from alcohol or opium. Those who do not employ nature’s narcotic but free themselves of it by hurried, anxious breathing become restless and crave artificial narcotics.

[9] It has been found that it is injurious to rebreathe expired air containing one per cent of carbon dioxid, but a far greater percentage is harmless if introduced into fresh air, thus indicating that the injury from poor ventilation comes chiefly from the “crowd poison,” or organic particles thrown off.

=Fatigue without work= occurs with people who are idle. The oxidation in their cells is not complete, and poisonous products of the incomplete burning result. This is known as self-poisoning (auto-toxemia). The poisons are taken by the blood to the nerves and brain, and give a tired feeling as effectually as does hard work; or the food may ferment in the food tube and form poisons which increase the tired feeling. Such persons are usually irritable, while persons who are fatigued by useful labor are likely to be dull and drowsy.

[Illustration: FIG. 118.--THE SITUATION OF HEADACHES with reference to their causes.]

=Headaches= are caused by poisons in the blood or by pressure of blood congested in the head. Like all other pains they should be a source of benefit in that they show us ways of living to be shunned in the future. Many persons, however, not only derive no profit from a headache, but by unwise efforts to cure the pain, bring permanent injury to themselves in addition to the suffering of the headache.

_Bromides_, _opium_, and other _poisons_ deaden and weaken the nervous system while preventing the headache from being felt. _Headache powders_, phenacetin, acetanelid, antikamnia, and other vile poisons made from coal tar, shock and weaken the heart and reduce the vital activities so that the headache is no longer felt. In consequence of shocks from repeated doses of such drugs, the heart will not work so well, and may give way some time in the future when an effort or strain makes unusual demands upon it. Their use has made heart disease more prevalent. The liver and kidney cells and the white corpuscles have to destroy and remove the drugs. Many people are foolish enough to injure their bodies and risk death rather than suffer pain or avoid pain by prudent living.

_Sick headaches are foretold_ by a dull feeling, sleepiness after eating, a coated tongue, and constipation. It would be better to remove the undigested, spoiled food from the stomach (four glasses of water will cause vomiting) than to take a drug. At the first indication of trouble, abstain from eating, or use a fruit diet for twenty-four hours, and drink water freely. This will enable the body to dispose of the excess of waste matter.

=The Highest Living Medical Authority on Drugs.=--Dr. Osler, formerly of Johns Hopkins University and now of Oxford University, says:

“But the new school does not feel itself under obligation to give any medicines whatever, while a generation ago not only could few physicians have held their practice unless they did, but few would have thought it safe or scientific. Of course there are still many cases where the patient or the patient’s friends must be humored by administering medicine, or alleged medicine, where it is not really needed, and indeed often where the buoyancy of mind, which is the real curative agent, can only be created by making him wait hopefully for the expected action of medicine; and some physicians still cannot unlearn their old training. But the change is great. The modern treatment of disease relies very greatly on the old so-called natural methods, diet and exercise, bathing and massage, in other words giving the natural forces the fullest scope by easy and thorough nutrition, increased flow of blood, and removal of obstructions to the excretory systems or the circulation in the tissues. One notable example is typhoid fever. At the outset of the nineteenth century it was treated with “remedies” of the extremest violence,--bleeding and blistering, vomiting and purging, antimony and calomel, and other heroic remedies. Now the patient is bathed and nursed and carefully tended, but rarely given medicine. This is the result partly of the remarkable experiments of the Paris and Vienna schools into the action of drugs which have shaken the stoutest faiths; and partly of the constant and reproachful object lesson of homeopathy. No regular physician would ever admit that the homeopathic “infinitesimals” could do any good as direct curative agents; and yet it was perfectly certain that homeopaths lost no more of their patients than others. There was but one conclusion to draw, that most drugs had no effect whatever on the diseases for which they were administered.”--“Encyclopædia Americana,” Vol. X. (Munn & Co., New York.)

=Applying Hygienic Tests Systematically.=--The cause of ill health (_e.g._ a headache) should be sought with system and thoroughness, applying the tests in rotation to every function of the body: _Lungs._ Is the air habitually breathed fresh and free from dust? Is the body held up, and is the chest or waist cramped by clothing? _Muscles._ Is enough physical exertion made to cause deep breaths to be drawn? _Food._ Is it simple, digestible, and eaten properly? _Drink._ Is the water pure? _Cleanliness_, _Work and Rest_, _Clothing_, _Ventilation_, and _Mental State_ may be inquired into until the source of trouble is found and the cause of ill health removed. To give drugs and leave the cause of ill health untouched, is to fail. There are signs of coming weakness or illness which, if heeded and the ways of living improved, will usually prevent illness. Among these signs are headaches, paleness, sensitiveness to cold, heavy feeling or pain after meals, constipation. Huxley says that young people should so learn physiology and so understand their bodies that they will _heed the first sign of nature’s displeasure, and not wait for a box on the ear_.

=Nervous Children.=--A report on the health of the school children in one of our large cities shows that one third of the children in those schools have some disorder of the nerves. Nervousness (weakened control of the nerves) may show itself by sluggishness of mind, great _irritability of temper_, frequent _spells of the_ “_blues_,” or by _involuntary movements_ of a _jerky_ or fidgety kind. Sound development of city children’s nerves is hindered because of the constant noise in cities both day and night; by _shortening of the hours of sleep_; by _excessive use of sugar_ for food; by living much among people with _no chance to be alone and let the nerves rest_, and among boys by the _use of cigarettes_.

=How to Prevent the School from injuring Children.=--(1) _Ventilation_ is of first importance. Breathing the breath of fifty other children does far more harm than overstudy. (2) _The time devoted to work_ should not be long, especially in the lower grades (no study out of school). (3) The _work should be diversified_; not only printed words, but pictures, natural objects, and the outdoor world should be studied. (4) The teacher and parent should see that _the habitual poise_ of the child is favorable to health. (5) The children should be _encouraged to play_. Running games at recess are of the greatest value, and are as indispensable to the health of a boy or girl as of a colt. (6) _Physical exercise_ should be provided at short intervals between lessons, especially _stretching exercises_ and _movements that straighten the spine and hips and elevate the chest_.

=The Effect of Alcohol upon Nerve Function.=--In attacking the nerve centers, alcohol begins with the cerebrum, the highest, and proceeds toward the lowest. Hence as a man becomes drunk he first talks foolishly (cerebrum affected), then he staggers (cerebellum affected), and he finally goes to sleep and breathes very hard (medulla affected) in a drunken stupor. It rarely happens that the breathing center is completely disabled and the man dies from the strong poison. The greatest evil of alcohol is seen in the case of steady drinking. This gradually destroys the soundness of the nervous system and weakens self-control. The tendency with nearly all drinkers is to increase the amount taken.

=Not Total Abstainers, but the Advocates of Universal Moderation are the Visionaries.=--The evil results from alcohol are so great as to be almost incredible. The plainest statements of its effects are sometimes denounced as unscientific by persons prejudiced in its favor. A part of the two billion dollars annually paid for liquors is used in influencing public opinion through the press.

PRACTICAL QUESTIONS.--=1.= Why does travel often cure a sick person when all else fails? =2.= Why is working more healthful than “taking exercise”? (p. 47.) =3.= Is it better for children to play or to take exercise? =4.= Why can one walk and carry on a conversation at the same time? (p. 127.) =5.= How does indigestion cause a headache? (p. 133.) =6.= Does perfectly comfortable clothing from head to foot help to make one at ease in company? Does uncomfortable clothing tend to make one awkward? =7.= Why is it as important to have the shoes and clothes perfectly comfortable when going out as when staying at home? =8.= When one’s finger is cut, where is the pain? =9.= In what two ways may opening a window when a student is becoming dull and drowsy at his books enable him to wake up and study with ease? =10.= What kinds of cells shrivel like a baked apple when they become fatigued? (Fig. 117.) =11.= A nerve or nerve fiber can hardly become tired or fatigued, for the nerve cell supplies the energy. What do we mean when we say the nerves are worn out? (Fig. 117.) =12.= Why do you throw cold water upon a fainting person? =13.= Why does constant, moderate drinking undermine the health more than occasional intoxication? =14.= Why does stoppage of the circulation cause one to faint? (See Chap. VI.) =15.= Why is grazing the skin often more painful than cutting it? (Colored Fig. 1.) =16.= Why do the lower animals always act upon sudden impulse? What part of the brain enables man to retain sensations and not act upon them until later? =17.= Does “nervousness” more probably indicate a bright mind or a high temper? =18.= What is the effect of a cold bath upon the nerves? (Chap. II.) =19.= Did you ever know a cigarette smoker whose hand trembled? =20.= Need there be any fear of a sobbing child holding its breath until it dies? =21.= Why is muscle tone greater in cold weather?

=The True Function of Stimulants.=--One whose heart has nearly given out because of exposure to severe weather may be temporarily revived by alcohol. _It will not be wise to do so unless it is certain that a warm fire and protection will be reached before the reaction comes._ Much less would be necessary to revive an abstainer than a drunkard. _Habitually_ disturbing the body with stimulants makes them ineffective in a time of emergency. A cup of coffee will not keep a watcher awake if he is used to coffee.

=Definitions: Stimulant, Narcotic, Poison.=--_A stimulant is anything that excites the body to activity, but is of no help or of insignificant help, in replacing the strength used up._

_A narcotic is anything that deadens or dulls the nervous system._ It comes from a word meaning “to benumb.”

_Poisons_ are active substances, which, taken in quantities, as man takes food, destroy life; in smaller quantities they injure the body and may destroy life. Alcohol is a poison. Wine, beer, whisky, contain varying quantities of it.

=The Narcotic and Stimulant Effects of Poisons.=--Examples of poisons are alcohol, nicotin, opium, arsenic, strychnin. Poisons excite the body when taken in small doses, while in large doses they produce paralysis and death. _The irritating or stimulating effect is due to_ derangement of the functions or to the efforts of the cells to free the body of the destructive substance. _The narcotic effect is due to_ the poison having so benumbed the nerves and injured the cells that their activities cease, or become less for a time. You readily see how the same poison can be both a stimulant and a narcotic: _the stimulating effect always comes first, followed by the stupefying effect_. If the dose is very small, the stimulating effect will last longer; if it is large, the narcotic effect is greater and felt more quickly. A habit of using stimulants is an invariable sign of weakness. The first dose of morphine or cocaine may be the first step in a lifelong blight of strength and happiness. If physicians whose treatment of a case results in leaving a patient with a drug or alcohol habit were sued for malpractice, they would be less reckless. The annual consumption of morphine is estimated at twenty-seven grains per capita in China, and fifty grains in the United States.

=Reaction.=--_This is the depressed and exhausted condition that comes on after a period of unnatural activity._ It follows the exciting effects of a stimulant.

=Natural Stimulants.=--If there were nothing to arouse activity, life would be impossible. A cold wind is a natural stimulant. _The activity aroused by a cold wind is just enough to help the body withstand the cold; artificial stimulants cause an expenditure having no relation to the needs of the body._ Hence there is a great waste of energy. Feelings may stimulate, as love for his family may stimulate a man to labor. The desire for knowledge may stimulate a boy to study. Hunger may stimulate a man to eat. Hunger is a natural stimulant, and is not likely to make him eat to excess; tea, coffee, pepper, etc., arouse a false appetite. These things are used chiefly for their stimulant effect, for they contain little or no nourishment. We will now study about artificial stimulants. _Such stimulants always cause an unregulated and unhealthy action, and are always followed by reaction._

=How much Strength is stored in the Body?=--Dr. Tanner of Minnesota believed that most people eat too much. _Another physician said that no human being could go forty days without food._ Dr. Tanner made the experiment. He lost thirty-six pounds in weight, but he weighed 121¹⁄₂ pounds and had considerable strength at the end of the forty days. The first thing he ate at the close of his fast was the juice of a ripe watermelon.

Once some miners were shut in by the caving of a part of a mine. But, unlike the case just described, _they were without water as well as food_. When, by digging, the rescuers reached them seven days after, several were still found alive, although most of them had died. The miners, no doubt, had nourishment in their bodies for some weeks more of life, but the body lacked water to dissolve it and bring it within the reach of the cells most needing it.

=A Stupendous Fact.=--These incidents show how wisely the body is made, and prove that the cells store up nourishment for weeks ahead. _The large amount of nourishment stored in the human body_ is one of the most striking and important facts with which the science of physiology has to deal, and it should be borne in mind, or we may make great mistakes about some very simple matters and especially in regard to the effects of stimulants.

=Foolish Rashness.=--Did you ever get so tired that you had to give up and stop, however much you would have liked to continue at work or play? _To rest was the wise thing to do._ Because you know there is much energy stored in the body, this need not tempt you to go on until you almost break down. Probably you know _people who are conceited about their bodies_ and say they are “made of cast iron”; that nothing can hurt them. Such conceit will be almost sure to get its possessor into trouble.

=How a Safeguard may be broken down.=--It is a very wise arrangement that, _under ordinary conditions, we cannot get at the surplus energy we have_. Carbon dioxid and other wastes accumulate in the tissues and paralyze the nerves. Fatigue and other feelings compel us to be provident, as it were; yet stimulants and narcotics, by irritating the nerve cells, arouse them and cause us to expend some of this reserve energy. Thus man is enabled to get at this precious store which he should save for emergencies, when he is sick and cannot digest food, or when he is making some mighty effort. A weak, ill man who has eaten very little for weeks, when delirious is sometimes so powerful that it takes several strong men to hold him in bed. But the delirious mania often uses up the little energy left, and costs the man his life.

=The only source of energy for man’s body= is the union of food and oxygen; he must get his energy from the same source that the engine does; and this is from his food, which serves as fuel, and the oxygen which burns it. If one has been working hard preparing for examinations, or gathering hay, or in attending to some important business, or has been under the excitement of some pleasure trip, and _feels “blue” and worn out, then let him bear the result like a man_, or like a true boy or girl, as the case may be. Giving up for a while, or “toughing it out” with the blues, or losing a little time from business, will not hurt, but will restore strength, while a stimulant will leave him less of a man than before.

=Nervousness.=--The attempt to divide the race into brain workers, muscle workers, and loafers, whether men or women, is a powerful factor in race degeneration. Leonard Hill says: “Hysteria and nervous exhaustion are the fruits not of overwork, but of lack of varied and interesting employment. The absurd opinion that hard work is menial and low, leads to most pernicious consequences. The girl who, turning from brain work to manual labor, can cook, scrub, wash, and garden, invites the bloom of health to her cheeks; while the fine do-nothing lady loses her good looks, suffers from the blues, and is a nuisance to her friends and a misery to herself.” A Japanese lady holds views similar to those of Dr. Hill. Read footnote.[10]

[10] =Statement by Madame Toyi Niku= of Yeddo, Japan, after a six months’ visit to the United States.--“Worry and inactivity, it seems to me, sharply mark the women of your middle classes. I did not attempt to study your leaders of society, for they are much alike the world over--the same fuss, the same display of jewels and finery, the same scandals, the same uselessness. Your women do not diversify enough. If they are good cooks, they stop there; perhaps another is a good housekeeper, another can sew finely; but doing one thing makes narrow-mindedness. In Japan we strive to do many things. The worry troubles of your women, it seems to me, come largely from improper eating and overeating. I have sat at many of your tables and there is too much food on them and too much variety. First, women overeat, then they doctor, then they starve, and then they become nervous. A woman’s diet, especially a mother’s, should always be simple. Cut down eating and increase variety of labor and exercise. My own people live that way with a result that we have better feminine bodies, better skins, and better tempers than your women. I like the brightness of your young women. Perhaps you will take the hideous hats off them some day, find a substitute for the bad corset, and let them wear clothes that are loose, yet are soft and clinging. They are bound up in their clothes too much now and their judgment of colors and combinations is not good. Their clothing is either garish or very dull in hue. The simplest girl in Japan knows how to harmonize color with herself.”--_Mother’s Magazine_, November, 1907.

SUBJECTS FOR DEBATE.--(1) Does the Chinese woman deform her body less than the Caucasian woman and suffer less from it? (2) Does as much disease originate in the dining room as the barroom? (3) Are drugs a necessary evil? (4) Does pride cause as much illness as ignorance? (5) Is it ever right to neglect the health? (6) Does the mind or the way of living have more effect upon the health?

=Disuse and Degeneration.=--Many persons in civilized countries cherish a vain hope of having sound muscles without habitual use of them, pure blood without deep breathing, a strong circulation in an inactive body, a fresh skin without keeping the body sound, a hearty appetite without enough physical labor to use the food already eaten, steady nerves with a part of the body overworked and a part stagnating from disuse. Their flabby muscles, pale skins, highly seasoned food to arouse appetite, narcotics to deaden irritable nerves, and the wide use of drugs as a fancied substitute for right living all show the attempt to be a miserable failure. If the parents leading such a life escape with fairly good health and average length of life, they leave a few unhealthy children in whom physical degeneration is plain. Complete, balanced living only prevents degeneration. Although there are cases of illness which are not necessarily a disgrace, disease usually originates in weakness of character or lack of common sense. The snob who thinks himself above physical labor, the dupes who at the bidding of avaricious fashion mongers think more of clothes than of a free body, the narrow, unbalanced man, who concentrates all his energies on one ambition, the short-sighted one who worries, all grow into a diseased state.