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  • 1897
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not think of anything else. It would take all our time to attend to living. Hence the care of such delicate and important machinery has wisely been put beyond our control.

Thus, too, these muscles act instinctively without training; but the voluntary need long and careful education. A babe can use the muscles of swallowing on the first day of its life as well as it ever can. But as it grows up, long and patient education of its voluntary muscles is needed to achieve walking, writing, use of musical instruments, and many other acts of daily life.

[Illustration: Fig. 32.–A Spindle Cell of Involuntary Muscle. (Highly magnified.)]

Experiment 18. _To show the general appearance of the muscles._ Obtain the lower part of a sheep’s or calf’s leg, with the most of the lean meat and the hoof left on. One or more of the muscles with their bundles of fibers, fascia, and tendons; are readily made out with a little careful dissection. The dissection should be made a few days before it is wanted and the parts allowed to harden somewhat in dilute alcohol.

68. Properties of Muscular Tissue. The peculiar property of living muscular tissue is irritability, or the capacity of responding to a stimulus. When a muscle is irritated it responds by contracting. By this act the muscle does not diminish its bulk to any extent; it simply changes its form. The ends of the muscle are drawn nearer each other and the middle is thicker.

Muscles do not shorten themselves all at once, but the contraction passes quickly over them in the form of a wave. They are usually stimulated by nervous action. The delicate nerve fibrils which end in the fibers communicate with the brain, the center of the will power. Hence, when the brain commands, a nervous impulse, sent along the nerve fibers, becomes the exciting stimulus which acts upon the muscles and makes them shorter, harder, and more rigid.[10]

Muscles, however, will respond to other than this usual stimulus. Thus an electrical current may have a similar effect. Heat, also, may produce muscular contraction. Mechanical means, such as a sharp blow or pinching, may irritate a muscle and cause it to contract.

We must remember that this property of contraction is inherent and belongs to the muscle itself. This power of contraction is often independent of the brain. Thus, on pricking the heart of a fish an hour after removal from its body, obvious contraction will occur. In this case it is not the nerve force from the brain that supplies the energy for contraction. The power of contraction is inherent in the muscle substance, and the stimulus by irritating the nerve ganglia of the heart simply affords the opportunity for its exercise.

Contraction is not, however, the natural state of a muscle. In time it is tired, and begins to relax. Even the heart, the hardest-working muscle, has short periods of rest between its beats. Muscles are highly elastic as well as contractile. By this property muscle yields to a stretching force, and returns to its original length if the stretching has not been excessive.

[Illustration: Fig. 33.–Principal Muscles of the Body. (Anterior view.)]

69. The Object of Contraction. The object of contraction is obvious. Like rubber bands, if one end of a muscle be fixed and the other attached to some object which is free to move, the contraction of the muscle will bring the movable body nearer to the fixed point. A weight fastened to the free end of a muscle may be lifted when the muscle contracts. Thus by their contraction muscles are able to do their work. They even contract more vigorously when resistance is opposed to them than when it is not. With increased weight there is an increased amount of work to be done. The greater resistance calls forth a greater action of the muscle. This is true up to a certain point, but when the limit has been passed, the muscle quickly fails to respond.

Again, muscles work best with a certain degree of rapidity provided the irritations do not follow each other too rapidly. If, however, the contractions are too rapid, the muscles become exhausted and fatigue results. When the feeling of fatigue passes away with rest, the muscle recovers its power. While we are resting, the blood is pouring in fresh supplies of building material.

Experiment 19. _To show how muscles relax and contract_. Lay your left forearm on a table; grasp with the right hand the mass of flesh on the front of the upper arm. Now gradually raise the forearm, keeping the elbow on the table. Note that the muscle thickens as the hand rises. This illustrates the contraction of the biceps, and is popularly called “trying your muscle” Reverse the act. Keep the elbow in position, bring the forearm slowly to the table, and the biceps appears to become softer and smaller,–it relaxes.

Experiment 20. Repeat the same experiment with other muscles. With the right hand grasp firmly the extended left forearm. Extend and flex the fingers vigorously. Note the effect on the muscles and tendons of the forearm. Grasp with the right hand the calf of the extended right leg, and vigorously flex the leg, bringing it near to the body. Note the contractions and relaxations of the muscles.

70. Arrangement of Muscles. Muscles are not connected directly with bones. The mass of flesh tapers off towards the ends, where the fibers pass into white, glistening cords known as tendons. The place at which a muscle is attached to a bone, generally by means of a tendon, is called its origin; the end connected with the movable bone is its insertion.

There are about 400 muscles in the human body, all necessary for its various movements. They vary greatly in shape and size, according to their position and use. Some are from one to two feet long, others only a fraction of an inch. Some are long and spindle-shaped, others thin and broad, while still others form rings. Thus some of the muscles of the arm and thigh are long and tapering, while the abdominal muscles are thin and broad because they help form walls for cavities. Again, the muscular fibers which surround and by their contraction close certain orifices, as those of the eyelids and lips, often radiate like the spokes of a wheel.

Muscles are named according to their shape, position, division of origin or insertion, and their function. Thus we have the _recti_ (straight), and the _deltoid_ (Δ, delta), the _brachial_ (arm), _pectoral_ (breast), and the _intercostals_ (between the ribs), so named from their position. Again, we have the _biceps_ (two-headed), _triceps_ (three-headed), and many others with similar names, so called from the points of origin and insertion. We find other groups named after their special use. The muscles which bend the limbs are called _flexors_ while those which straighten them are known as _extensors_.

After a bone has been moved by the contraction of a muscle, it is brought back to its position by the contraction of another muscle on the opposite side, the former muscle meanwhile being relaxed. Muscles thus acting in opposition to each other are called antagonistic. Thus the biceps serves as one of the antagonists to the triceps, and the various flexors and extensors of the limbs are antagonistic to one another.

71. The Tendons. The muscles which move the bones by their contraction taper for the most part, as before mentioned, into tendons. These are commonly very strong cords, like belts or straps, made up of white, fibrous tissue.

Tendons are most numerous about the larger joints, where they permit free action and yet occupy but little space. Large and prominent muscles in these places would be clumsy and inconvenient. If we bend the arm or leg forcibly, and grasp the inside of the elbow or knee joint, we can feel the tendons beneath the skin. The numerous tendons in the palm or on the back of the hand contribute to its marvelous dexterity and flexibility. The thickest and strongest tendon in the body is the tendon of Achilles, which connects the great muscles in the calf of the leg with the heel bone (sec. 49).

When muscles contract forcibly, they pull upon the tendons which transmit the movement to the bones to which they are attached. Tendons may be compared to ropes or cords which, when pulled, are made to act upon distant objects to which one end is fastened. Sometimes the tendon runs down the middle of a muscle, and the fibers run obliquely into it, the tendon resembling the quill in a feather. Again, tendons are spread out in a flat layer on the surface of muscles, in which case they are called aponeuroses. Sometimes a tendon is found in the middle of a muscle as well as at each end of it.

[Illustration: Fig. 34.–The Biceps Muscle dissected to show its Tendons.]

72. Synovial Sheaths and Sacs. The rapid movement of the tendons over bony surfaces and prominences would soon produce an undue amount of heat and friction unless some means existed to make the motion as easy as possible. This is supplied by sheaths which form a double lining around the tendons. The opposed surfaces are lined with synovial membrane,[11] the secretion from which oils the sheaths in which the tendons move.

Little closed sacs, called synovial sacs or bursæ, similarly lined and containing fluid, are also found in special places between two surfaces where much motion is required. There are two of these bursæ near the patella, one superficial, just under the skin; the other deep beneath the bone (Fig. 29). Without these, the constant motion of the knee-pan and its tendons in walking would produce undue friction and heat and consequent inflammation. Similar, though smaller, sacs are found over the point of the elbow, over the knuckles, the ankle bones, and various other prominent points. These sacs answer a very important purpose, and are liable to various forms of inflammation.

Experiment 21. Examine carefully the tendons in the parts dissected in Experiment 18. Pull on the muscles and the tendons, and note how they act to move the parts. This may be also admirably shown on the leg of a fowl or turkey from a kitchen or obtained at the market.

Obtain the hoof of a calf or sheep with one end of the tendon of Achilles still attached. Dissect it and test its strength.

73. Mechanism of Movement. The active agents of bodily movements, as we have seen, are the muscles, which by their contraction cause the bones to move one on the other. All these movements, both of motion and of locomotion, occur according to certain fixed laws of mechanics. The bones, to which a great proportion of the muscles in the body are attached, act as distinct levers. The muscles supply the power for moving the bones, and the joints act as fulcrums or points of support. The weight of the limb, the weight to be lifted, or the force to overcome, is the resistance.

74. Levers in the Body. In mechanics three classes of levers are described, according to the relative position of the power, the fulcrum, and the resistance. All the movements of the bones can be referred to one or another of these three classes.

Levers of the first class are those in which the fulcrum is between the power and the weight. The crowbar, when used to lift a weight at one end by the application of power at the other, with a block as a fulcrum, is a familiar example of this class. There are several examples of this in the human body. The head supported on the atlas is one. The joint between the atlas and the skull is the fulcrum, the weight of the head is the resistance. The power is behind, where the muscles from the neck are attached to the back of the skull. The object of this arrangement is to keep the head steady and balanced on the spinal column, and to move it backward and forward.

[Illustration: Fig. 35.–Showing how the Bones of the Arm serve as Levers.

P, power;
W, weight;
F, fulcrum.

Levers of the second class are those in which the weight is between the fulcrum and the power. A familiar example is the crowbar when used for lifting a weight while one end rests on the ground. This class of levers is not common in the body. Standing on tiptoe is, however, an example. Here the toes in contact with the ground are the fulcrum, the power is the action of the muscles of the calf, and between these is the weight of the body transmitted down the bones of the leg to the foot.

Levers of the third class are those in which the power is applied at a point between the fulcrum and weight. A familiar example is where a workman raises a ladder against a wall. This class of levers is common in the body. In bending the forearm on the arm, familiarly known as “trying your muscle,” the power is supplied by the biceps muscle attached to the radius, the fulcrum is the elbow joint at one end of the lever, and the resistance is the weight of the forearm at the other end.

Experiment 22. _To illustrate how the muscles use the bones as levers._ First, practice with a ruler, blackboard pointer, or any other convenient object, illustrating the different kinds of levers until the principles are familiar. Next, illustrate these principles on the person, by making use of convenient muscles. Thus, lift a book on the toes, by the fingers, on the back of the hand, by the mouth, and in other ways.

These experiments, showing how the bones serve as levers, may be multiplied and varied as circumstances may require.

75. The Erect Position. The erect position is peculiar to man. No other animal naturally assumes it or is able to keep it long. It is the result of a somewhat complex arrangement of muscles which balance each other, some pulling backwards and some forwards. Although the whole skeleton is formed with reference to the erect position, yet this attitude is slowly learned in infancy.

In the erect position the center of gravity lies in the joint between the sacrum and the last lumbar vertebra. A line dropped from this point would fall between the feet, just in front of the ankle joints. We rarely stand with the feet close together, because that basis of support is too small for a firm position. Hence, in all efforts requiring vigorous muscular movements the feet are kept more or less apart to enlarge the basis of support.

Now, on account of the large number and flexibility of the joints, the body could not be kept in an upright position without the cooperation of certain groups of muscles. The muscles of the calf of the leg, acting on the thigh bone, above the knee, keep the body from falling forward, while another set in front of the thigh helps hold the leg straight. These thigh muscles also tend to pull the trunk forward, but in turn are balanced by the powerful muscles of the lower back, which help keep the body straight and braced.

The head is kept balanced on the neck partly by the central position of the joint between the atlas and axis, and partly by means of strong muscles. Thus, the combined action of these and other muscles serves to balance the body and keep it erect. A blow on the head, or a sudden shock to the nervous system, causes the body to fall in a heap, because the brain has for the time lost its power over the muscles, and they cease to contract.

[Illustration: Fig. 36.–Diagram showing the Action of the Chief Muscles which keep the Body Erect. (The arrows indicate the direction in which these muscles act, the feet serving as a fixed basis.) [After Huxley.]

_Muscles which tend to keep the body from falling forward._

A, muscles of the calf;
B, of the back of the thigh;
C, of the spinal column.

_Muscles which tend to keep the body from falling backward._

D, muscles of the front of the leg;
E, of the front of the thigh;
F, of the front of the abdomen;
G, of the front of the neck.

76. Important Muscles. There are scores of tiny muscles about the head, face, and eyes, which, by their alternate contractions and relaxations, impart to the countenance those expressions which reflect the feelings and passions of the individual. Two important muscles, the temporal, near the temples, and the masseter, or chewing muscle, are the chief agents in moving the lower jaw. They are very large in the lion, tiger, and other flesh-eating animals. On the inner side of each cheek is the buccinator, or trumpeter’s muscle, which is largely developed in those who play on wind instruments. Easily seen and felt under the skin in thin persons, on turning the head to one side, is the sterno-cleido-mastoid muscle, which passes obliquely down on each side of the neck to the collar bone–prominent in sculpture and painting.

The chest is supplied with numerous muscles which move the ribs up and down in the act of breathing. A great, fan-shaped muscle, called the pectoralis major, lies on the chest. It extends from the chest to the arm and helps draw the arm inward and forward. The arm is raised from the side by a large triangular muscle on the shoulder, the deltoid, so called from its resemblance to the Greek letter delta, Δ. The biceps, or two-headed muscle, forms a large part of the fleshy mass in front of the arm. Its use is to bend the forearm on the arm, an act familiarly known as “trying your muscle.” Its direct antagonist is the three-headed muscle called the triceps. It forms the fleshy mass on the back of the arm, its use being to draw the flexed forearm into a right line.

On the back and outside of the forearm are the extensors, which straighten the wrist, the hand, and the fingers. On the front and inside of the forearm are the flexors, which bend the hand, the wrist, and the fingers. If these muscles are worked vigorously, their tendons can be readily seen and felt under the skin. At the back of the shoulder a large, spread-out muscle passes upward from the back to the humerus. From its wide expanse on the back it is known as the latissimus dorsi (broadest of the back). When in action it draws the arm downward and backward, or, if one hangs by the hands, it helps to raise the body. It is familiarly known as the “climbing muscle.”

[Illustration: Fig. 37.–A Few of the Important Muscles of the Back.]

Passing to the lower extremity, the thigh muscles are the largest and the most powerful in the body. In front a great, four-headed muscle, quadriceps extensor, unites into a single tendon in which the knee-cap is set, and serves to straighten the knee, or when rising from a sitting posture helps elevate the body. On the back of the thigh are several large muscles which bend the knee, and whose tendons, known as the “hamstrings,” are readily felt just behind the knee. On the back of the leg the most important muscles, forming what is known as the calf, are the gastrocnemius and the soleus. The first forms the largest part of the calf. The soleus, so named from resembling a sole-fish, is a muscle of broad, flattened shape, lying beneath the gastrocnemius. The tendons of these two muscles unite to form the tendon of Achilles, as that hero is said to have been invulnerable except at this point. The muscles of the calf have great power, and are constantly called into use in walking, cycling, dancing, and leaping.

77. The Effect of Alcoholic Drinks upon the Muscles. It is found that a man can do more work without alcohol than with it. After taking it there may be a momentary increase of activity, but this lasts only ten or fifteen minutes at the most. It is followed by a rapid reduction of power that more than outweighs the momentary gain, while the quality of the work is decidedly impaired from the time the alcohol is taken.

Even in the case of hard work that must be speedily done, alcohol does not help, but hinders its execution. The tired man who does not understand the effects of alcohol often supposes that it increases his strength, when in fact it only deadens his sense of fatigue by paralyzing his nerves. When put to the test he is surprised at his self-deception.

Full intoxication produces, by its peculiar depression of the brain and nervous system, an artificial and temporary paralysis of the muscles, as is obvious in the pitifully helpless condition of a man fully intoxicated. But even partial approach to intoxication involves its proportionate impairment of nervous integrity, and therefore just so much diminution of muscular force. All athletes recognize this fact, as while training for a contest, rigid abstinence is the rule, both from liquors and tobacco. This muscular weakness is shown also in the unsteady hand, the trembling limbs of the inebriate, his thick speech, wandering eye, and lolling head.

78. Destructive Effect of Alcoholic Liquors upon Muscular Tissue. Alcoholic liquors retard the natural chemical changes so essential to good health, by which is meant the oxidation of the nutritious elements of food. Careful demonstration has proved also that the amount of carbon dioxide escaping from the lungs of intoxicated persons is from thirty to fifty per cent less than normal. This shut-in carbon stifles the nervous energy, and cuts off the power that controls muscular force. This lost force is in close ratio to the retained carbon: so much perverted chemical change, so much loss of muscular power. Not only the strength but the fine delicacy of muscular action is lost, the power of nice control of the hand and fingers, as in neat penmanship, or the use of musical instruments.

To this perverted chemical action is also due the fatty degeneration so common in inebriates, affecting the muscles, the heart, and the liver. These organs are encroached upon by globules of fat (a hydrocarbon), which, while very good in their proper place and quantity, become a source of disorder and even of death when they abnormally invade vital structures. Other poisons, as phosphorus, produce this fatty decay more rapidly; but alcohol causes it in a much more general way.

This is proved by the microscope, which plainly shows the condition mentioned, and the difference between the healthy tissues and those thus diseased.

[Illustration: Fig. 38.–Principal Muscles on the Left Side of Neck.

A, buccinator;
B, masseter;
C, depressor anguli oris;
D, anterior portion of the digastric; E, mylo-hyoid;
F, tendon of the digastric;
G, sterno-hyoid;
H, sterno-thyroid;
K, omo-hyoid;
L, sternal origin of sterno-cleido-mastoid muscle; M, superior fibers of deltoid;
N, posterior scalenus;
O, clavicular origin of sterno-cleido-mastoid; P, sterno-cleido-mastoid;
R, trapezius;
S, anterior constrictor;
T, splenius capitis;
V, stylo-hyoid;
W, posterior portion of the digastric; X, fasciculi of ear muscles;
Z, occipital.

[NOTE. It was proposed during the Civil War to give each soldier in a certain army one gill of whiskey a day, because of great hardship and exposure. The eminent surgeon, Dr. Frank H. Hamilton of New York, thus expressed his views of the question: “It is earnestly desired that no such experiment will ever be repeated in the armies of the United States. In our own mind, the conviction is established, by the experience and observation of a life, that the regular routine employment of alcoholic stimulants by man in health is never, under any circumstances, useful. We make no exceptions in favor of cold or heat or rain.”

“It seems to me to follow from these Arctic experiences that the regular use of spirits, even in moderation, under conditions of great physical hardship, continued and exhausting labor, or exposure to severe cold cannot be too strongly deprecated.”

A. W. Greely, retired Brigadier General, U.S.A., and formerly leader of the Greely Expedition.]

79. Effect of Tobacco on the Muscles. That other prominent narcotic, tobacco, impairs the energy of the muscles somewhat as alcohol does, by its paralyzing effect upon the nervous system. As all muscular action depends on the integrity of the nervous system, whatever lays its deadening hand upon that, saps the vigor and growth of the entire frame, dwarfs the body, and retards mental development. This applies especially to the young, in the growing age between twelve or fourteen and twenty, the very time when the healthy body is being well knit and compacted.

Hence many public schools, as well as our national naval and military academies, rigidly prohibit the use of tobacco by their pupils. So also young men in athletic training are strictly forbidden to use it.[12] This loss of muscular vigor is shown by the unsteady condition of the muscles, the trembling hand, and the inability to do with precision and accuracy any fine work, as in drawing or nice penmanship.

Additional Experiments.

Experiment 23. _ To examine the minute structure of voluntary muscular fiber._ Tease, with two needles set in small handles, a bit of raw, lean meat, on a slip of glass, in a little water. Continue until the pieces are almost invisible to the naked eye.

Experiment 24. Place a clean, dry cover-glass of about the width of the slip, over the water containing the torn fragments. Absorb the excess of moisture at the edge of the cover, by pressing a bit of blotting-paper against it for a moment. Place it on the stage of a microscope and examine with highest obtainable power, by light reflected upward from the mirror beneath the stage. Note the apparent size of the finest fibers; the striation of the fibers, or their markings, consisting of alternate dim and bright cross bands. Note the arrangement of the fibers in bundles, each thread running parallel with its neighbor.

Experiment 25. _To examine the minute structure of involuntary muscular fiber, a tendon, or a ligament._ Obtain a very small portion of the muscular coat of a cow’s or a pig’s stomach. Put it to soak in a solution of one dram of bichromate of potash in a pint of water. Take out a morsel on the slip of glass, and tease as directed for the voluntary muscle. Examine with a high power of the microscope and note: (1) the isolated cells, long and spindle-shaped, that they are much flattened; (2) the arrangement of the cells, or fibers, in sheets, or layers, from the torn ends of which they project like palisades.

Experiment 26. Tease out a small portion of the tendon or ligament in water, and examine with a glass of high power. Note the large fibers in the ligament, which branch and interlace.

Experiment 27. With the head slightly bent forwards, grasp between the fingers of the right hand the edge of the left sterno-cleido-mastoid, just above the collar bone. Raise the head and turn it from left to right, and the action of this important muscle is readily seen and felt. In some persons it stands out in bold relief.

Experiment 28. The tendons which bound the space (popliteal) behind the knee can be distinctly felt when the muscles which bend the knee are in action. On the outer side note the tendons of the biceps of the leg, running down to the head of the fibula. On the inside we feel three tendons of important muscles on the back of the thigh which flex the leg upon the thigh.

Experiment 29. _To show the ligamentous action of the muscles._ Standing with the back fixed against a wall to steady the pelvis, the knee can be flexed so as to almost touch the abdomen. Take the same position and keep the knee rigid. When the heel has been but slightly raised a sharp pain in the back of the thigh follows any effort to carry it higher. Flexion of the leg to a right angle, increases the distance from the lines of insertion on the pelvic bones to the tuberosities of the tibia by two or three inches–an amount of stretching these muscle cannot undergo. Hence the knee must be flexed in flexion of the hip.

Experiment 30. A similar experiment may be tried at the wrist. Flex the wrist with the fingers extended, and again with the fingers in the fist. The first movement can be carried to 90°, the second only to 30°, or in some persons up to 60°. Making a fist had already stretched the extensor muscles of the arm, and they can be stretched but little farther. Hence, needless pain will be avoided by working a stiff wrist with the parts loose, or the fingers extended, and not with a clenched fist.

Review Analysis: Important Muscles.

Name. Chief Function.

Head and Neck.

Occipito-frontalis. moves scalp and raises eye brow. Orbicularis palpebrarum. shuts the eyes. Levator palpebrarum. opens the eyes. Temporal. raise the lower jaw.
Masseter. ” ” ” “
Sterno-cleido-mastoid. depresses head upon neck and neck upon chest. Platysma myoides. depresses lower jaw and lower lip.


Pectoralis major. draws arm across front of chest. Pectoralis minor. depresses point of shoulder, Latissimus dorsi. draws arm downwards and backwards. Serratus magnus. assists in raising ribs. Trapezius. Rhomboideus. backward movements of head and shoulder, Intercostals. raise and depress the ribs. External oblique. /various forward movements Internal oblique. \ of trunk
Rectus abdominis. compresses abdominal viscera and acts upon pelvis.

Upper Limbs.

Deltoid. carries arm outwards and upwards. Biceps. flexes elbow and raises arm. Triceps. extends the forearm.
Brachialis anticus. flexor of elbow. Supinator longus. flexes the forearm. Flexor carpi radialis. flexors of wrist. Flexor carpi ulnaris. ” ” “

Lower Limbs.

Gluteus maximus. adducts the thigh. Adductors of thigh. draw the leg inwards. Sartorius. crosses the legs.
Rectus femoris. flexes the thigh. Vastus externus. extensor of leg.
Vastus internus. extensor of leg upon thigh. Biceps femoris. flexes leg upon thigh. Gracilis. flexes the leg and adducts thigh. Tibialis anticus. draws up inner border of foot. Peroneus longus. raises outer edge of foot, Gastrocnemius. keep the body erect, and Soleus. aid in walking and running.

Chapter IV.

Physical Exercise.

80. Importance of Bodily Exercise. Nothing is so essential to success in life as sound physical health. It enables us to work with energy and comfort, and better to endure unusual physical and mental strains. While others suffer the penalties of feebleness, a lower standard of functional activities, and premature decay, the fortunate possessor of a sound mind in a sound body is better prepared, with proper application, to endure the hardships and win the triumphs of life[13].

This element of physical capacity is as necessary to a useful and energetic life, as are mental endowment and intellectual acquirement. Instinct impels us to seek health and pleasure in muscular exercise. A healthy and vigorous child is never still except during sleep. The restless limbs and muscles of school children pent up for several hours, feel the need of movement, as a hungry man craves food. This natural desire for exercise, although too often overlooked, is really one of the necessities of life. One must be in ill health or of an imperfect nature, when he ceases to feel this impulse. Indeed, motion within proper bounds is essential to the full development and perfect maintenance of the bodily health. Unlike other machines, the human body becomes within reasonable limits, stronger and more capable the more it is used.

As our tenure of life at best is short, it is our duty to strive to live as free as possible from bodily ills. It is, therefore, of paramount importance to rightly exercise every part of the body, and this without undue effort or injurious strain.

Strictly speaking, physical exercise refers to the functional activity of each and every tissue, and properly includes the regulation of the functions and movements of the entire body. The word exercise, however, is used usually in a narrower sense as applied to those movements that are effected by the contraction of the voluntary muscles.

Brief reference will be made in this chapter only to such natural and systematic physical training as should enter into the life of every healthy person.

81. Muscular Activity. The body, as we have learned, is built up of certain elementary tissues which are combined to make bones, muscles, nerves, and other structures. The tissues, in turn, are made up of countless minute cells, each of which has its birth, lives its brief moment to do its work in the animal economy, is separated from the tissue of which it was a part, and is in due time eliminated by the organs of excretion,–the lungs, the skin, or the kidneys. Thus there is a continuous process of growth, of decay, and removal, among the individual cells of each tissue.

[NOTE. The Incessant Changes in Muscular Tissue. “In every tiny block of muscle there is a part which is really alive, there are parts which are becoming alive, there are parts which have been alive, and are now dying or dead; there is an upward rush from the lifeless to the living, a downward rush from the living to the dead. This is always going on, whether the muscle be quiet and at rest, or whether it be active and moving,–some of the capital of living material is being spent, changed into dead waste; some of the new food is always being raised into living capital. But when the muscle is called upon to do work, when it is put into movement, the expenditure is quickened, there is a run upon the living capital, the greater, the more urgent the call for action.”–Professor Michael Foster.]

These ceaseless processes are greatly modified by the activity of the bodily functions. Every movement of a muscle, for instance, involves change in its component cells. And since the loss of every atom of the body is in direct relation to its activity, a second process is necessary to repair this constant waste; else the body would rapidly diminish in size and strength, and life itself would soon end. This process of repair is accomplished, as we shall learn in Chapters VI. and VII., by the organs of nutrition, which convert the food into blood.

[Illustration: Fig. 39.–Showing how the Muscles of the Back may be developed by a Moderate Amount of Dumb-Bell Exercise at Home. (From a photograph.)]

82. Effect of Exercise upon the Muscles. Systematic exercise influences the growth and structure of the muscles of the body in a manner somewhat remarkable. Muscular exercise makes muscular tissue; from the lack of it, muscles become soft and wasted. Muscles properly exercised not only increase in size, both as a whole and in their individual structure, but are better enabled to get rid of material which tends to hamper their movements. Thus muscular exercise helps to remove any needless accumulation of fat, as well as useless waste matters, which may exist in the tissues. As fat forms no permanent structural part of the organism, its removal is, within limits, effected with no inconvenience.

Muscular strength provides the joints with more powerful ligaments and better developed bony parts. After long confinement to the bed from disease, the joints have wasted ligaments, thin cartilages, and the bones are of smaller proportions. Duly exercised muscles influence the size of the bones upon which they act. Thus the bones of a well-developed man are stronger, firmer, and larger than those of a feeble person.

He who has been physically well trained, has both a more complete and a more intelligent use of his muscles. He has acquired the art of causing his muscles to act in concert. Movements once difficult are now carried on with ease. The power of coördination is increased, so that a desired end is attained with the least amount of physical force and nervous energy. In learning to row, play baseball, ride the bicycle, or in any other exercises, the beginner makes his movements in a stiff and awkward manner. He will use and waste more muscular force in playing one game of ball, or in riding a mile on his wheel, than an expert would in doing ten times the work. He has not yet learned to balance one set of muscles against their antagonists.

[Illustration: Fig. 40.–The Standard Special Chest Weight.

A convenient machine by means of which all the muscles of the body may be easily and pleasantly exercised with sufficient variations in the movements to relieve it of monotony.

A space 6 ft wide, 6 ft deep, and 7 ft high nearly in front of the machine is required for exercise.]

In time, however, acts which were first done only with effort and by a conscious will, become automatic. The will ceases to concern itself. By what is called reflex action, memory is developed in the spinal cord and the muscular centers (sec. 273). There is thus a great saving of actual brain work, and one important cause of fatigue is removed.

83. Effect of Exercise on Important Organs. The importance of regular exercise is best understood by noting its effects upon the principal organs of the body. As the action of the heart is increased both in force and frequency during exercise, the flow of blood throughout the body is augmented. This results from the force of the muscular contractions which play their part in pressing the blood in the veins onward towards the heart. Exercise also induces a more vigorous respiration, and under increased breathing efforts the lung capacity is increased and the size of the chest is enlarged. The amount of air inspired and expired in a given time is much larger than if the body were at rest. The blood is thus supplied with a much larger amount of oxygen from the air inhaled, and gives off to the air a corresponding excess of carbon dioxid and water.

Again, exercise stimulates and strengthens the organs of digestion. The appetite is improved, as is especially noted after exercise in the open air. The digestion is more complete, absorption becomes more rapid, the peristaltic movements of the bowels are promoted, and the circulation through the liver is more vigorous. More food is taken to supply the force necessary for the maintenance of the mechanical movements. Ample exercise also checks the tendency towards a torpid circulation in the larger digestive organs, as the stomach and the liver, so common with those who eat heartily, but lead sedentary lives. In short, exercise may be regarded as a great regulator of nutrition.

Exercise increases the flow of blood through the small vessels of the skin, and thus increases the radiation of heat from the surface. If the exercise be vigorous and the weather hot, a profuse sweat ensues, the rapid evaporation of which cools the body. The skin is thus a most important regulator of the bodily temperature, and prevents any rise above the normal which would otherwise result from vigorous exercise. (See secs. 226 and 241).

84. Effect of Exercise upon the Personal Appearance. Judicious and systematic exercise, if moderately employed, soon gives a more upright and symmetrical figure, and an easier and more graceful carriage. Rounded shoulders become square, the awkward gait disappears, and there is seen a graceful poise to the head and a bearing of the body which mark those whose muscles have been well trained. A perfectly formed skeleton and well-developed muscles give the graceful contour and perfect outline to the human body. The lean, soft limbs of those who have never had any physical education, often look as if they belonged to persons recovering from sickness. The effects of sound physical exercise are well exhibited in the aspect of the neck, shoulders, and chest of one who has been well trained. This is noticeable in gymnasts and others who practice upon the horizontal bar, with chest weights, dumb-bells, and other apparatus which develop more especially the muscles of the upper half of the trunk.

[Illustration: Fig. 41.–Young Woman practicing at Home with the “Whitely Exerciser.” (From a photograph)]

Exercise improves the condition of the tissues generally. They become more elastic, and in all respects sounder. The skin becomes firm, clear, and wholesome. Hence, every part of the surface of the body rapidly takes on a change in contour, and soon assumes that appearance of vigor and soundness which marks those of firm physical condition. The delicate, ruddy aspect of the complexion, the swing about the body and the bearing of the head and shoulders, of young women whose physical training has been efficient, are in marked contrast with those characteristics in persons whose education in this respect has been neglected.

85. Effect of Unsuitable or Excessive Exercise. But exercise, like everything else which contributes to our welfare, may be carried to excess. The words excessive and unsuitable, when applied to muscular exertion, are relative terms, and apply to the individual rather than to amount of work done. Thus what may be excessive for one person, might be suitable and beneficial to another. Then the condition of the individual, rather than the character of the muscular work, is always a most important factor.

Breathlessness is, perhaps, the most common effect of undue exertion. Let a middle-aged person, who is out of practice, run a certain distance, and he is soon troubled with his breathing. The respirations become irregular, and there is a sense of oppression in his chest. He pants, and his strength gives out. His chest, and not his legs, has failed him. He is said to be “out of breath.” He might have practiced dumb-bells or rowed for some time without inconvenience.

The heart is often overstrained, and at times has been ruptured during violent exertion, as in lifting an immense weight. The various forms of heart-disease are common with those whose occupations involve severe muscular effort, as professional athletes and oarsmen. Hæmorrhages of various kinds, especially from the lungs, or rupture of blood-vessels in the brain, are not uncommon results of over-exertion.

Excessive repetition of muscular movements may lead to permanent contractions of the parts involved. Thus sailors, mechanics, and others frequently develop a rigidity of the tendons of the hand which prevents the full extension of the fingers. So stenographers, telegraphers and writers occasionally suffer from permanent contractions of certain muscles of the arm, known as writer’s cramp, due to their excessive use. But the accidents which now and then may result from severe physical exertion, should discourage no one from securing the benefits which accrue from moderate and reasonable exercise.

86. Muscular Fatigue. We all know how tiresome it is to hold the arm outstretched horizontally even for a few moments. A single muscle, the deltoid, in this case does most of the work. Even in a vigorous man, this muscle can act no longer than four to six minutes before the arm drops helpless. We may prolong the period by a strong effort of the will, but a time soon comes when by no possible effort are we able to hold out the arm. The muscle is said to be fatigued. It has by no means lost its contractile power, for if we apply a strong electric stimulus to it, the fatigue seems to disappear. Thus we see the functional power of a muscle has a definite limit, and in fatigue that limit is reached.

[Illustration: Fig. 42.–A Well-Equipped Gymnasium. (From a photograph.)]

The strength of the muscle, its physical condition, the work it has done, and the mental condition of the individual, all modify the state of fatigue. In those difficult acts which involve a special effort of the will, the matter of nerve exhaustion is largely concerned. Thus, the incessant movements in St. Vitus’ dance result in comparatively little fatigue, because there is no association of the brain with the muscular action. If a strong man should attempt to perform voluntarily the same movements, he would soon have to rest. None of the movements which are performed independently of the will, as the heart-beats and breathing movements, ever involve the sensation of fatigue. As a result of fatigue the normal irritability of muscular tissue becomes weakened, and its force of contraction is lessened. There is, also, often noticed in fatigue a peculiar tremor of the muscles, rendering their movements uncertain. The stiffness of the muscles which comes on during severe exercise, or the day after, are familiar results of fatigue.

This sense of fatigue should put us on guard against danger. It is a kind of regulator which serves in the ordinary actions of life to warn us not to exceed the limits of useful exercise. Fatigue summons us to rest long before all the force of the motor organs has been expended, just as the sensation of hunger warns us that we need food, long before the body has become weak from the lack of nourishment.

We should never forget that it is highly essential to maintain an unused reserve of power, just as a cautious merchant always keeps at the bank an unexpended balance of money. If he overspends his money he is bankrupt, and the person who overspends his strength is for the time physically bankrupt. In each case the process of recovery is slow and painful.

87. Rest for the Muscles. Rest is necessary for the tissues, that they may repair the losses sustained by work; that is, a period of rest must alternate with a period of activity. Even the heart, beating ceaselessly, has its periods of absolute rest to alternate with those of work. A steam-engine is always slowly, but surely, losing its fitness for work. At last it stops from the need of repair. Unlike the engine, the body is constantly renewing itself and undergoing continual repair. Were it not for this power to repair and renew its various tissues, the body would soon be worn out.

This repair is really a renovation of the structure. Rest and work are relative terms, directly opposed to each other. Work quickens the pulse and the respiration, while rest slows both. During sleep the voluntary muscles are relaxed, and those of organic life work with less energy. The pulse and the respiration are less frequent, and the temperature lower than when awake. Hence sleep, “tired Nature’s sweet restorer,” may be regarded as a complete rest.

The periods of rest should vary with the kind of exercise. Thus exercise which produces breathlessness requires frequent but short rests. The trained runner, finding his respiration embarrassed, stops a moment to regain his breath. Exercises of endurance cause fatigue less quickly than those of speed, but require longer rest. Thus a man not used to long distances may walk a number of hours without stopping, but while fatigue is slow to result, it is also slow to disappear. Hence a lengthy period of rest is necessary before he is able to renew his journey.

88. Amount of Physical Exercise Required. The amount of physical exercise that can be safely performed by each person, is a most important and practical question. No rule can be laid down, for what one person bears well, may prove very injurious to another. To a certain extent, each must be guided by his own judgment. If, after taking exercise, we feel fatigued and irritable, are subject to headache and sleeplessness, or find it difficult to apply the mind to its work, it is plain that we have been taxing our strength unduly, and the warnings should be heeded.

Age is an important factor in the problem, as a young man may do with ease and safety, what might be injurious to an older person. In youth, when the body is making its most active development, the judicious use of games, sports, and gymnastics is most beneficial. In advanced life, both the power and the inclination for exercise fail, but even then effort should be made to take a certain reasonable amount of exercise.

Abundant evidence shows that physical development is most active from thirteen to seventeen years of age; this manifests itself clearly by increase in weight. Hence this period of life is of great consequence. If at this age a boy or girl is subjected to undue physical strain, the development may suffer, the growth be retarded, and the foundation laid for future ill health.

[Illustration: Fig. 43.–Student exercising in the School Gymnasium on the Rowing Machine. (From a photograph.)]

The proper amount of exercise must vary greatly with circumstances. It may be laid down as a fairly safe rule, that a person of average height and weight, engaged in study or in any indoor or sedentary occupation, should take an amount of exercise equivalent to walking five or six miles a day. Growing children, as a rule, take more exercise than this, while most men working indoors take far less, and many women take less exercise than men. Exercise may be varied in many ways, the more the better; but for the most part it should always be taken in the open air.

89. Time for Exercise. It is not prudent to do hard work or take severe exercise, just before or just after a full meal. The best time is one or two hours after a meal. Vigorous exercise while the stomach is busily digesting food, may prove injurious, and is apt to result sooner or later in dyspepsia. On the other hand, severe exercise should not be taken on an empty stomach. Those who do much work or study before breakfast, should first take a light lunch, just enough to prevent any faint feeling. With this precaution, there is no better time for moderate exercise than the early morning.

In the case of children, physical exercises should not be undertaken when they are overtired or hungry. Neither is it judicious for adults to take vigorous exercise in the evening, after a long and arduous day’s work.

90. Walking, Running, and Jumping. Walking is generally regarded as the simplest and most convenient mode of taking exercise. Man is essentially a walking animal. When taken with a special object in view, it is the best and most pleasant of all physical activities. It is suited for individuals of all ages and occupations, and for residents of every climate. The child, the athlete, and the aged are all able to indulge in this simple and effective means of keeping the body in health.

In walking, the muscles of the entire body are brought into action, and the movements of breathing and the circulation of the blood are increased. The body should be erect, the chest thrown out, the head and shoulders held back, and the stride long and elastic. It is an excellent custom to add to the usefulness of this fine exercise, by deep, voluntary inhalations of pure air.

Running is an excellent exercise for children and young people, but should be sparingly indulged in after the age of thirty-five. If it be accompanied with a feeling of faintness, breathlessness, and palpitation of the heart, the exercise is too severe, and its continuance may do serious harm. Running as an exercise is beneficial to those who have kept themselves in practice and in sound condition. It brings into play nearly every muscle of the body, and thus serves to develop the power of endurance, as well as strength and capacity for rapid movement.

Jumping may well be left to boys and young men under twenty, but skipping with a rope, allied to jumping, is an admirable and beneficial form of exercise. It brings into action many muscles without putting undue strain upon any particular group.

91. Skating, Swimming, and Rowing. Skating is a delightful and invigorating exercise. It calls into play a great variety of muscles, and is admirably adapted for almost all ages. It strengthens the ankles and helps give an easy and graceful carriage to the body. Skating is especially valuable, as it can be enjoyed when other out-door exercises are not convenient.

Every child above ten years of age should be taught to swim. The art, once mastered, is never forgotten. It calls into use a wide combination of muscles. This accomplishment, so easily learned, should be a part of our education, as well as baseball or bicycling, as it may chance to any one to save his own life or that of a companion.

In many respects rowing is one of the most perfect exercises at our command. It expands the chest, strengthens the body, and gives tone to the muscles of the abdomen. It is very suitable for girls and women, as no other exercise is so well adapted to remedy the muscular defects so marked in their sex. Even elderly persons can row day after day without difficulty. The degree of muscular effort required, can be regulated so that those with weak hearts and weak lungs can adjust themselves to the exercise.

92. Bicycling as an Exercise. The bicycle as a means of taking exercise has come into popular use with remarkable rapidity. Sharp competition bids fair to make the wheel more popular and less expensive than ever. Its phenomenal use by persons of all ages and in all stations of life, is proof of the enthusiasm with which this athletic exercise is employed by women as well as by men.

Mechanical skill has removed most of the risks to health and person which once existed. A good machine, used by its owner with judgment, is the most convenient, the safest, and the least expensive means of traveling for pleasure or exercise. It is doing more than any other form of exercise to improve the bodily condition of thousands whose occupations confine them all day to sedentary work. Dependent upon no one but himself, the cyclist has his means of exercise always at hand. No preparation is necessary to take a spin of ten miles or so on the road, during a summer evening or before breakfast.

Bicycling brings into active use the muscles of the legs as well as those of the trunk and arms. It seems to benefit those who suffer from dyspepsia, constipation, and functional disorders of the liver.

A special caution must be used against overdoing in cycling, for the temptation by rivalry, making a record, by social competition on the road, is stronger in this form of exercise than in any other, especially for young folks. Many cases have occurred of permanent injury, and even loss of life, from collapse simply by excessive exertion and exhaustion.

93. Outdoor Games and Physical Education. While outdoor games are not necessary to maintain health, yet we can scarcely overestimate the part that the great games of baseball, football, tennis, golf, and croquet, play in the physical development of young people. When played in moderation and under suitable conditions, they are most useful and beneficial exercises. They are played in the open air, and demand a great variety of vigorous muscular movement, with a considerable amount of skill and adroitness of action. These games not only involve healthful exercise, but develop all those manly and wholesome qualities so essential to success in life.

A vigorous body is well-nigh essential to success, but equally important are readiness of action, sound judgment, good temper, personal courage, a sense of fair play, and above all, a spirit of honor. Outdoor games, when played in a reasonable and honorable manner, are most efficient and practical means to develop these qualities in young people.

94. The School and Physical Education. The advantages to be derived, during the school period, from the proper care and development of the body, should be understood and appreciated by school officials, teachers, and parents. The school period is the best time to shape the lives of pupils, not mentally or morally alone, but physically as well. This is the time, by the use of a few daily exercises at school, to draw back the rounding shoulders, to form the habit of sitting and standing erect, to build up strong and comely arms and chests, and otherwise to train pupils to those methods which will serve to ripen them into vigorous and well-knit men and women.

Teachers can by a little effort gain the knowledge requisite properly to instruct their pupils in a few systematic exercises. Gratifying results will follow just as the teacher and pupils evince interest and judgment in the work. It is found by experience that pupils are not only quick to learn, but look forward eagerly to the physical exercises as an interesting change from the routine of school life.

There should be a stated time for these school exercises, as for any other duty. There can be practiced in the schoolroom a great variety of interesting and useful exercises, which call for little or no expense for apparatus. Such exercises should no more interfere with the children’s usual games than any other study does. Under no circumstances should the play hours be curtailed.

95. Physical Exercises in School. Physical exercises of some sort, then, should be provided for pupils in our schools, especially in large towns and cities, where there is little opportunity for outdoor games, and they should form a part of the regular course of study. The object should be the promotion of sound health rather than the development of muscle, or performing feats of agility or strength. Exercises with dumb-bells and wands, or even without any apparatus, practiced a few times a day, for five minutes at a time, do a great deal of good. They relax the tension of body and mind, and introduce an element of pleasure into the routine of school life. They increase the breathing power and quicken the action of the heart.

[Illustration: Fig. 44.–Physical Exercises as carried on in Schools. (From photographs.)]

[NOTE. “In early boyhood and youth nothing can replace the active sports so much enjoyed at this period; and while no needless restrictions should be placed upon them, consideration should be paid to the amount, and especially to the character, of the games pursued by delicate youth. For these it would be better to develop the weakened parts by means of systematic physical exercises and by lighter sports.”–Dr. John M. Keating on “Physical Development” in Pepper’s _Cyclopædia of the Diseases of Children_.]

If vigorously and systematically carried out, these exercises invigorate all the tissues and organs of the body, and stimulate them to renewed activity. They serve to offset the lack of proper ventilation, faulty positions at the desks, and the prolonged inaction of the muscles. To secure the greatest benefit from physical training in school, it is important that the pupils be interested in these exercises, and consider them a recreation, and not a task[14].

96. Practical Points about Physical Exercise. The main object in undertaking systematic and graduated physical exercises is not to learn to do mere feats of strength and skill, but the better to fit the individual for the duties and the work of life. Exercises should be considered with reference to their availability from the learner’s standpoint. The most beneficial exercises ordinarily are the gentle ones, in which no strain is put upon the heart and the respiration. The special aim is to secure the equal use of all the muscles, not the development of a few. The performance of feats of strength should never come within the scope of any educational scheme. Exercises which call for sustained effort, violent exertion, or sudden strain are best avoided by those who have had no preparation or training.

Regular exercise, not sudden and occasional prolonged exertion, is necessary for health. The man or woman who works in an office or store all the week, and on Sunday or a holiday indulges in a long spin on the bicycle, often receives more harm than good from the exertion. Exercise should be taken, so far as is convenient, in the open air, or in a large and well-ventilated room.[15]

After the more violent exercises, as baseball, football, a long ride on the bicycle, or even after a prolonged walk, a warm bath should be taken at the first convenient opportunity. Care should be taken to rub down thoroughly, and to change a part or all of the clothing. Exercise is comparatively valueless until the idea of taking it for health is quite forgotten in the interest and pleasure excited by the occasion. No exercise should be carried to such a degree as to cause fatigue or exhaustion. Keep warmly clad after exercise, avoid chills, and always stop exercising as soon as fatigue is felt.

Wear clothing which allows free play to all the muscles of the body. The clothing should be light, loose, and made of wool. Care should be taken not to take cold by standing about in clothes which are damp with perspiration. In brisk walking and climbing hills keep the mouth shut, especially in cold weather, and breathe through the nose, regulating the pace so that it can be done without discomfort.

97. Effect of Alcoholic Liquors and Tobacco upon Physical Culture. As a result of the unusual attention given to physical culture in the last few years, hundreds of special instructors are now employed in training young people in the theory and practice of physical exercise. These expert teachers, to do their work with thoroughness and discipline, recognize the necessity of looking after the daily living of their students. The time of rising and retiring, the hours of sleep, the dress, the care of the diet, and many other details of personal health become an important part of the training.

Recognizing the fact that alcoholic drink and tobacco are so disastrous to efficiency in any system of physical training, these instructors rigidly forbid the use of these drugs under all circumstances. While this principle is perhaps more rigorously enforced in training for athletic contests, it applies equally to those who have in view only the maintenance of health.

Books on Physical Education. There are many excellent books on physical education, which are easily obtained for reading or for reference. Among these one of the most useful and suggestive is Blackie’s well-known book, “How to Get Strong and how to Stay so.” This little book is full of kindly advice and practical suggestions to those who may wish to begin to practice health exercises at home with inexpensive apparatus. For more advanced work, Lagrange’s “Physiology of Bodily Exercise” and the Introduction to Maclaren’s “Physical Education” may be consulted. A notable article on “Physical Training” by Joseph H. Sears, an Ex-Captain of the Harvard Football Team, may be found in Roosevelt’s “In Sickness and in Health.”

Price lists and catalogues of all kinds of gymnastic apparatus are easily obtained on application to firms handling such goods.

Various Systems of Physical Exercises. The recent revival of popular interest in physical education has done much to call the attention of the public to the usefulness and importance of a more thorough and systematic use of physical exercises, both at home and in the schools. It is not within the scope of this book to describe the various systems of gymnastic and calisthenic exercises now in common use in this country. For the most part they have been modified and rearranged from other sources, notably from the two great systems, i.e., Swedish and German.

For a most comprehensive work on the Swedish system, the teacher is referred to the “Swedish System of Educational Gymnastics,” with 264 illustrations, by Baron Nils Posse. There is also a small manual for teachers, called “Handbook of School Gymnastics of the Swedish Systems,” by the same author.

Chapter V.

Food and Drink.

98. Why we need Food. The body is often compared to a steam-engine in good working order. An engine uses up fuel and water to obtain from them the energy necessary to do its work. So, we consume within our bodies certain nutritious substances to obtain from them the energy necessary for our activities. Just as the energy for the working of the engine is obtained from steam by the combustion of fuel, so the energy possessed by our bodies results from the combustion or oxidation within us of the food we eat. Unless this energy is provided for the body it will have but little power of doing work, and like an engine without steam, must soon become motionless.

99. Waste and Repair. A steam-engine from the first stroke of its piston-rod begins to wear out, and before long needs repair. All work involves waste. The engine, unless kept in thorough repair, would soon stop. So with our bodies. In their living cells chemical changes are constantly going on; energy, on the whole, is running down; complex substances are being broken up into simpler combinations. So long as life lasts, food must be brought to the tissues, and waste products carried away from them. It is impossible to move a single muscle, or even to think for one moment, without some minute part of the muscular or brain tissue becoming of no further use in the body. The transformation of dead matter into living tissue is the ever-present miracle which life presents even in its lowest forms.

In childhood the waste is small, and the amount of food taken is more than sufficient to repair the loss. Some of the extra food is used in building up the body, especially the muscles. As we shall learn in Chapter VIII., food is also required to maintain the bodily heat. Food, then, is necessary for the production of energy, for the repair of the body, for the building up of the tissues, and for the maintenance of bodily heat.

100. Nature of the Waste Material. An ordinarily healthy person passes daily, on an average, by the kidneys about 50 ounces of waste material, of which 96 per cent is water, and from the intestines, on an average, 5½ ounces, a large proportion of which is water. By the skin, in the shape of sweat and insensible perspiration, there is cast out about 23 ounces, of which 99 per cent is water; and by the lungs about 34 ounces, 10 of which are water and the remainder carbon dioxid.

Now if we omit an estimate of the undigestible remains of the food, we find that the main bulk of what daily leaves the body consists of water, carbon dioxid, and certain solid matters contained in solution in the renal secretion and the sweat. The chief of these solid matters is urea, a complex product made up of four elements,–carbon, hydrogen, oxygen, and nitrogen. Water contains only two elements, hydrogen and oxygen; and carbon dioxid also has only two, carbon and oxygen. Hence, what we daily cast out of our bodies consists essentially of these four elements in the form mainly of water, carbon dioxid, and urea.

These waste products represent the oxidation that has taken place in the tissues in producing the energy necessary for the bodily activities, just as the smoke, ashes, clinkers, and steam represent the consumption of fuel and water in the engine. Plainly, therefore, if we could restore to the body a supply of these four elements equivalent to that cast out, we could make up for the waste. The object of food, then, is to restore to the body an amount of the four elements equal to that consumed. In other words, and briefly: The purpose of food is to supply the waste of the tissues and to maintain the normal composition of the blood.

101. Classification of Foods. Foods may be conveniently divided into four great classes, to which the name food-stuffs or alimentary principles has been given. They correspond to the chief “proximate principles” of which the body consists. To one or the other of these classes all available foods belong[16]. The classification of food-stuffs usually given is as follows:

I. Proteids, or Nitrogenous Foods.
II. Starches and Sugars, or Carbohydrates. III. Fats and Oils.
IV. Inorganic or Mineral Foods,–Water, Salt.

102. Proteids; or Nitrogenous Foods. The proteids, frequently spoken of as the nitrogenous foods, are rich in one or more of the following organic substances: albumen, casein, fibrin, gelatine, myosin, gluten, and legumin.

The type of this class of foods is albumen, well known as the white of an egg. The serum of the blood is very rich in albumen, as is lean meat. The curd of milk consists mainly of casein. Fibrin exists largely in blood and flesh foods. Gelatine is obtained from the animal parts of bones and connective tissue by prolonged boiling. One of the chief constituents of muscular fiber is myosin. Gluten exists largely in the cereals wheat, barley, oats, and rye. The proteid principle of peas and beans is legumin, a substance resembling casein.

As the name implies, the proteids, or nitrogenous foods, contain nitrogen; carbohydrates and fats, on the contrary, do not contain nitrogen. The principal proteid food-stuffs are milk, eggs, flesh foods of all kinds, fish, and the cereals among vegetable foods. Peas and beans are rich in proteids. The essential use of the proteids to the tissues is to supply the material from which the new proteid tissue is made or the old proteid tissue is repaired. They are also valuable as sources of energy to the body. Now, as the proteid part of its molecule is the most important constituent of living matter, it is evident that proteid food is an absolute necessity. If our diet contained no proteids, the tissues of the body would gradually waste away, and death from starvation would result. All the food-stuffs are necessary in one way or another to the preservation of perfect health, but proteids, together with a certain proportion of water and inorganic salts, are absolutely necessary for the bare maintenance of animal life–that is, for the formation and preservation of living protoplasm.

103. Starches and Sugars. The starches, sugars, and gums, also known as carbohydrates, enter largely into the composition of foods of vegetable origin. They contain no nitrogen, but the three elements, carbon, hydrogen, and oxygen, the last two in the same proportion as in water. The starches are widely distributed throughout the vegetable kingdom. They are abundant in potatoes and the cereals, and in arrowroot, rice, sago, and tapioca. Starch probably stands first in importance among the various vegetable foods.

The sugars are also widely distributed substances, and include the cane, grape, malt, maple, and milk sugars. Here also belong the gums and cellulose found in fruit, cereals, and all vegetables which form the basis of the plant cells and fibers. Honey, molasses, and manna are included in this class.

The physiological value of the starches and sugars lies in the fact that they are oxidized in the body, and a certain amount of energy is thereby liberated. The energy of muscular work and of the heat of the body comes largely from the oxidation, or destruction, of this class of foods. Now, inasmuch as we are continually giving off energy from the body, chiefly in the form of muscular work and heat, it is evident that material for the production of this energy must be taken in the food. The carbohydrates constitute the bulk of our ordinary food.

104. Fats and Oils. These include not only the ordinary fats of meat, but many animal and vegetable oils. They are alike in chemical composition, consisting of carbon and hydrogen, with a little oxygen and no nitrogen. The principal kinds of fat used as food are the fat of meat, butter, suet, and lard; but in many parts of the world various vegetable oils are largely used, as the olive, palm, cotton seed, cocoanut, and almond.

The use of the fats in the body is essentially the same as that of the starches and sugars. Weight for weight they are more valuable than the carbohydrates as sources of energy, but the latter are more easily digested, and more easily oxidized in the body. An important use of fatty foods is for the maintenance of the bodily heat. The inhabitants of Arctic regions are thus enabled, by large use of the fat and oil from the animals they devour, to endure safely the severe cold. Then there is reason to believe that fat helps the digestion of other foods, for it is found that the body is better nourished when the fats are used as food. When more fat is consumed than is required to keep up the bodily heat and to yield working power, the excess is stored up in various parts of the body, making a sort of reserve fuel, which may be drawn upon at any future time.

105. Saline or Mineral Foods. All food contains, besides the substances having potential energy, as described, certain saline matters. Water and salts are not usually considered foods, but the results of scientific research, as well as the experience of life, show that these substances are absolutely necessary to the body. The principal mineral foods are salt, lime, iron, magnesia, phosphorus, potash, and water. Except common salt and water, these substances are usually taken only in combination with other foods.

These saline matters are essential to health, and when not present in due proportion nutrition is disturbed. If a dog be fed on food freed from all salines, but otherwise containing proper nutrients, he soon suffers from weakness, after a time amounting to paralysis, and often dies in convulsions.

About 200 grains of common salt are required daily by an adult, but a large proportion of this is in our food. Phosphate of lime is obtained from milk and meats, and carbonate of lime from the hard water we drink. Both are required for the bones and teeth. The salts of potash, which assist in purifying the blood, are obtained from vegetables and fruits. An iron salt is found in most foods, and sulphur in the yolk of eggs.

106. Water. Water is of use chiefly as a solvent, and while not strictly a food, is necessary to life. It enters into the construction of every tissue and is constantly being removed from the body by every channel of waste[17].

As a solvent water aids digestion, and as it forms about 80 per cent of the blood, it serves as a carrier of nutrient material to all the tissues of the body.

Important Articles of Diet.

107. Milk. The value of milk as a food cannot be overestimated. It affords nourishment in a very simple, convenient, and perfect form. It is the sole food provided for the young of all animals which nourish their young. It is an ideal food containing, in excellent proportions, all the four elements necessary for growth and health in earlier youth.

[Table: Composition of Food Materials. Careful analyses have been made of the different articles of food, mostly of the raw, or uncooked foods. As might be expected, the analyses on record differ more or less in the percentages assigned to the various constituents, but the following table will give a fair idea of the fundamental nutritive value of the more common foods:

In 100 parts Water Proteid Fat Carbohydrate Ash Digestible Cellulose Meat 76.7 20.8 1.5 0.3 — 1.3 Eggs 73.7 12.6 12.1 — — 1.1 Cheese 36-60 25-33 7-30 3-7 — 3.4 Cow’s Milk 87.7 3.4 3.2 4.8 — 0.7 Wheat Flour 13.3 10.2 0.9 74.8 0.3 0.5 Wheat Bread 35.6 7.1 0.2 55.5 0.3 1.1 Rye Flour 13.7 11.5 2.1 69.7 1.6 1.4 Rye bread 42.3 6.1 0.4 49.2 0.5 1.5 Rice 13.1 7.0 0.9 77.4 0.6 1.0 Corn 13.1 9.9 4.6 68.4 2.5 1.5 Macaroni 10.1 9.0 0.3 79.0 0.3 0.5 Peas and Beans 12-15 23-26 1½-2 49-54 4.7 2-3 Potatoes 75.5 2.0 0.2 20.6 0.7 1.0 Carrots 87.1 1.0 0.2 9.3 1.4 0.9 Cabbage 90 2.3 0.5 4-6 1-2 1.3 Fruit 84 0.5 — 10 4 0.5 ]

Cheese is the nitrogenous part of milk, which has been coagulated by the use of rennet. The curd is then carefully dried, salted, and pressed. Cheese is sometimes difficult of digestion, as on account of its solid form it is not easily acted upon by the digestive fluids.

108. Meats. The flesh of animals is one of our main sources of food. Containing a large amount of proteid, it is admirably adapted for building up and repairing the tissues of the body. The proportion of water is also high, varying from 50 to 75 per cent. The most common meats used in this country are beef, mutton, veal, pork, poultry, and game.

Beef contains less fat and is more nutritious than either mutton or pork. Mutton has a fine flavor and is easily digested. Veal and lamb, though more tender, are less easily digested. Pork contains much fat, and its fiber is hard, so that it is the most difficult to digest of all the meats. Poultry and game have usually a small proportion of fat, but are rich in phosphates and are valued for their flavor.

109. Eggs. Consisting of about two-thirds water and the rest albumen and fat, eggs are often spoken of as typical natural food. The white of an egg is chiefly albumen, with traces of fat and salt; the yolk is largely fat and salts. The yellow color is due partly to sulphur. It is this which blackens a silver spoon. Eggs furnish a convenient and concentrated food, and if properly cooked are readily digested.

110. Fish. Fish forms an important and a most nutritious article of diet, as it contains almost as much nourishment as butcher’s meat. The fish-eating races and classes are remarkably strong and healthy. Fish is less stimulating than meat, and is thus valuable as a food for invalids and dyspeptics. To be at its best, fish should be eaten in its season. As a rule shell-fish, except oysters, are not very digestible. Some persons are unable to eat certain kinds of fish, especially shell-fish, without eruptions on the skin and other symptoms of mild poisoning.

111. Vegetable Foods. This is a large and important group of foods, and embraces a remarkable number of different kinds of diet. Vegetable foods include the cereals, garden vegetables, the fruits, and other less important articles. These foods supply a certain quantity of albumen and fat, but their chief use is to furnish starches, sugars, acids, and salts. The vegetable foods indirectly supply the body with a large amount of water, which they absorb in cooking.

112. Proteid Vegetable Foods. The most important proteid vegetable foods are those derived from the grains of cereals and certain leguminous seeds, as peas and beans. The grains when ground make the various flours or meals. They contain a large quantity of starch, a proteid substance peculiar to them called gluten, and mineral salts, especially phosphate of lime. Peas and beans contain a smaller proportion of starch, but more proteid matter, called legumin, or vegetable casein. Of the cereal foods, wheat is that most generally useful. Wheat, and corn and oatmeal form most important articles of diet. Wheat flour has starch, sugar, and gluten–nearly everything to support life except fat.

Oatmeal is rich in proteids. In some countries, as Scotland, it forms an important article of diet, in the form of porridge or oatmeal cakes.

Corn meal is not only rich in nitrogen, but the proportion of fat is also large; hence it is a most important and nutritious article of food. Rice, on the other hand, contains less proteids than any other cereal grain, and is the least nutritious. Where used as a staple article of food, as in India, it is commonly mixed with milk, cheese, or other nutritious substances. Peas and beans, distinguished from all other vegetables by their large amount of proteids–excel in this respect even beef, mutton, and fish. They take the place of meats with those who believe in a vegetable diet.

113. Non-proteid Vegetable Foods. The common potato is the best type of non-proteid vegetable food. When properly cooked it is easily digested and makes an excellent food. It contains about 75 per cent of water, about 20 per cent of carbohydrates, chiefly starch, 2 per cent of proteids, and a little fat and saline matters. But being deficient in flesh-forming materials, it is unfit for an exclusive food, but is best used with milk, meat, and other foods richer in proteid substances. Sweet potatoes, of late years extensively used as food, are rich in starch and sugar. Arrowroot, sago, tapioca, and similar foods are nutritious, and easily digested, and with milk furnish excellent articles of diet, especially for invalids and children.

Explanation of the Graphic Chart. The graphic chart, on the next page, presents in a succinct and easily understood form the composition of food materials as they are bought in the market, including the edible and non-edible portions. It has been condensed from Dr. W. O. Atwater’s valuable monograph on “Foods and Diet.” This work is known as the Yearbook of the U.S. Department of Agriculture for 1894.

KEY: 1, percentage of nutrients; 2, fuel value of 1 pound in calories. The unit of heat, called a _calorie_, or gramme-degree, is the amount of heat which is necessary to raise one gramme (15.43 grains) of water one degree centigrade (1.8° Fahr.). A, round beef; B, sirloin beef; C, rib beef; D, leg of mutton; E, spare rib of pork; F, salt pork; G, smoked ham; H, fresh codfish; I, oysters; J, milk; K, butter; L, cheese; M, eggs; N, wheat bread; O, corn meal; P, oatmeal; Q, dried beans; R, rice; S, potatoes; T, sugar.

This table, among other things, shows that the flesh of fish contains more water than that of warm-blooded animals. It may also be seen that animal foods contain the most water; and vegetable foods, except potatoes, the most nutrients. Proteids and fats exist only in small proportions in most vegetables, except beans and oatmeal. Vegetable foods are rich in carbohydrates while meats contain none. The fatter the meat the less the amount of water. Thus very lean meat may be almost four-fifths water, and fat pork almost one-tenth water.

[Illustration: Fig. 45.–Graphic Chart of the Composition of Food Materials. Composition of Food Materials. Nutritive ingredients, refuse, and fuel value. ]

114. Non-proteid Animal Foods. Butter is one of the most digestible of animal fats, agreeable and delicate in flavor, and is on this account much used as a wholesome food. Various substitutes have recently come into use. These are all made from animal fat, chiefly that of beef, and are known as butterine, oleomargarine, and by other trade names. These preparations, if properly made, are wholesome, and may be useful substitutes for butter, from which they differ but little in composition.

115. Garden Vegetables. Various green, fresh, and succulent vegetables form an essential part of our diet. They are of importance not so much on account of their nutritious elements, which are usually small, as for the salts they supply, especially the salts of potash. It is a well-known fact that the continued use of a diet from which fresh vegetables are excluded leads to a disease known as scurvy. They are also used for the agreeable flavor possessed by many, and the pleasant variety and relish they give to the food. The undigested residue left by all green vegetables affords a useful stimulus to intestinal contraction, and tends to promote the regular action of the bowels.

116. Fruits. A great variety of fruits, both fresh and dry, is used as food, or as luxuries. They are of little nutritive value, containing, as they do, much water and only a small amount of proteid, but are of use chiefly for the sugar, vegetable acids, and salts they contain.

In moderate quantity, fruits are a useful addition to our regular diet. They are cooling and refreshing, of agreeable flavor, and tend to prevent constipation. Their flavor and juiciness serve to stimulate a weak appetite and to give variety to an otherwise heavy diet. If eaten in excess, especially in an unripe or an overripe state, fruits may occasion a disturbance of the stomach and bowels, often of a severe form.

117. Condiments. The refinements of cookery as well as the craving of the appetite, demand many articles which cannot be classed strictly as foods. They are called condiments, and as such may be used in moderation. They give flavor and relish to food, excite appetite and promote digestion. Condiments increase the pleasure of eating, and by their stimulating properties promote secretions of the digestive fluids and excite the muscular contractions of the alimentary canal.

The well-known condiments are salt, vinegar, pepper, ginger, nutmeg, cloves, and various substances containing ethereal oils and aromatics. Their excessive use is calculated to excite irritation and disorder of the digestive organs.

118. Salt The most important and extensively used of the condiments is common salt. It exists in all ordinary articles of diet, but in quantities not sufficient to meet the wants of the bodily tissues. Hence it is added to many articles of food. It improves their flavor, promotes certain digestive secretions, and meets the nutritive demands of the body. The use of salt seems based upon an instinctive demand of the system for something necessary for the full performance of its functions. Food without salt, however nutritious in other respects, is taken with reluctance and digested with difficulty.

Salt has always played an important and picturesque part in the history of dietetics. Reference to its worth and necessity abounds in sacred and profane history. In ancient times, salt was the first thing placed on the table and the last removed. The place at the long table, above or below the salt, indicated rank. It was everywhere the emblem of hospitality. In parts of Africa it is so scarce that it is worth its weight in gold, and is actually used as money. Torture was inflicted upon prisoners of state in olden times by limiting the food to water and bread, without salt. So intense may this craving for salt become, that men have often risked their liberty and even their lives to obtain it.

119. Water. The most important natural beverage is pure water; in fact it is the only one required. Man has, however, from the earliest times preferred and daily used a variety of artificial drinks, among which are tea, coffee, and cocoa.

All beverages except certain strong alcoholic liquors, consist almost entirely of water. It is a large element of solid foods, and our bodies are made up to a great extent of water. Everything taken into the circulating fluids of the body, or eliminated from them, is done through the agency of water. As a solvent it is indispensable in all the activities of the body.

It has been estimated that an average-sized adult loses by means of the lungs, skin, and kidneys about eighty ounces of water every twenty-four hours. To restore this loss about four pints must be taken daily. About one pint of this is obtained from the food we eat, the remaining three pints being taken as drink. One of the best ways of supplying water to the body is by drinking it in its pure state, when its solvent properties can be completely utilized. The amount of water consumed depends largely upon the amount of work performed by the body, and upon the temperature.

Being one of the essential elements of the body, it is highly important that water should be free from harmful impurities. If it contain the germs of disease, sickness may follow its use. Without doubt the most important factor in the spread of disease is, with the exception of impure air, impure water. The chief agent in the spread of typhoid fever is impure water. So with cholera, the evidence is overwhelming that filthy water is an all-powerful agent in the spread of this terrible disease.

120. Tea, Coffee, and Cocoa. The active principle of tea is called theine; that of coffee, caffeine, and of cocoa, theobromine. They also contain an aromatic, volatile oil, to which they owe their distinctive flavor. Tea and coffee also contain an astringent called tannin, which gives the peculiar bitter taste to the infusions when steeped too long. In cocoa, the fat known as cocoa butter amounts to fifty per cent.

121. Tea. It has been estimated that one-half of the human race now use tea, either habitually or occasionally. Its use is a prolific source of indigestion, palpitation of the heart, persistent wakefulness, and of other disorders. When used at all it should be only in moderation. Persons who cannot use it without feeling its hurtful effects, should leave it alone. It should not be taken on an empty stomach, nor sipped after every mouthful of food.

122. Coffee. Coffee often disturbs the rhythm of the heart and causes palpitation. Taken at night, coffee often causes wakefulness. This effect is so well known that it is often employed to prevent sleep. Immoderate use of strong coffee may produce other toxic effects, such as muscular tremors, nervous anxiety, sick-headache, palpitation, and various uncomfortable feelings in the cardiac region. Some persons cannot drink even a small amount of tea or coffee without these unpleasant effects. These favorite beverages are unsuitable for young people.

123. Cocoa. The beverage known as cocoa comes from the seeds of the cocoa-tree, which are roasted like the coffee berries to develop the aroma. Chocolate is manufactured cocoa,–sugar and flavors being added to the prepared seeds. Chocolate is a convenient and palatable form of highly nutritious food. For those with whom tea and coffee disagree, it may be an agreeable beverage. The large quantity of fat which it contains, however, often causes it to be somewhat indigestible.

124. Alcoholic Beverages. There is a class of liquids which are certainly not properly food or drink, but being so commonly used as beverages, they seem to require special notice in this chapter. In view of the great variety of alcoholic beverages, the prevalence of their use, and the very remarkable deleterious effects they produce upon the bodily organism, they imperatively demand our most careful attention, both from a physiological and an hygienic point of view.

125. Nature of Alcohol. The ceaseless action of minute forms of plant life, in bringing about the decomposition of the elaborated products of organized plant or animal structures, will be described in more detail (secs. 394-398).

All such work of vegetable organisms, whether going on in the moulding cheese, in the souring of milk, in putrefying meat, in rotting fruit, or in decomposing fruit juice, is essentially one of fermentation, caused by these minute forms of plant life. There are many kinds of fermentation, each with its own special form of minute plant life or micro-organism.

In this section we are more especially concerned about that fermentation which results from the decomposition of sweet fruit, plant, or other vegetable, juices which are composed largely of water containing sugar and flavoring matters.

This special form of fermentation is known as alcoholic or vinous fermentation, and the micro-organisms that cause it are familiarly termed alcoholic ferments. The botanist classes them as _Saccharomycetes_, of which there are several varieties. Germs of _Saccharomycetes_ are found on the surfaces and stems of fruit as it is ripening. While the fruit remains whole these germs have no power to invade the juice, and even when the skins are broken the conditions are less favorable for their work than for that of the moulds,[18] which are the cause of the rotting of fruit.

But when fruit is crushed and its juice pressed out, the _Saccharomycetes_ are carried into it where they cannot get the oxygen they need from the air. They are then able to obtain oxygen by taking it from the sugar of the juice. By so doing they cause a breaking up of the sugar and a rearrangement of its elements. Two new substances are formed in this decomposition of sugar, viz., carbon dioxid, which arises from the liquid in tiny bubbles, and alcohol, a poison which remains in the fermenting fluid.

Now we must remember that fermentation entirely changes the nature of the substance fermented. For all forms of decomposition this one law holds good. Before alcoholic fermentation, the fruit juice was wholesome and beneficial; after fermentation, it becomes, by the action of the minute germs, a poisonous liquid known as alcohol, and which forms an essential part of all intoxicating beverages.

Taking advantage of this great law of fermentation which dominates the realm of nature, man has devised means to manufacture various alcoholic beverages from a great variety of plant structures, as ripe grapes, pears, apples, and other fruits, cane juices, corn, the malt of barley, rye, wheat, and other cereals.

The process differs according to the substance used and the manner in which it is treated, but the ultimate outcome is always the same, viz., the manufacture of a beverage containing a greater or less proportion of alcoholic poison. By the process of _distillation_, new and stronger liquor is made. Beverages thus distilled are known as ardent spirits. Brandy is distilled from wine, rum from fermented molasses, and commercial alcohol mostly from whiskey.

The poisonous element in all forms of intoxicating drinks, and the one so fraught with danger to the bodily tissues, is the alcohol they contain. The proportion of the alcoholic ingredient varies, being about 50 per cent in brandy, whiskey, and rum, about 20 to 15 per cent in wines, down to 5 per cent, or less, in the various beers and cider; but whether the proportion of alcohol be more or less, the same element of danger is always present.

126. Effects of Alcoholic Beverages upon the Human System. One of the most common alcoholic beverages is wine, made from the juice of grapes. As the juice flows from the crushed fruit the ferments are washed from the skins and stems into the vat. Here they bud and multiply rapidly, producing alcohol. In a few hours the juice that was sweet and wholesome while in the grape is changed to a poisonous liquid, capable of injuring whoever drinks it. One of the gravest dangers of wine-drinking is the power which the alcohol in it has to create a thirst which demands more alcohol. The spread of alcoholism in wine-making countries is an illustration of this fact.

Another alcoholic beverage, common in apple-growing districts, is cider. Until the microscope revealed the ferment germ on the “bloom” of the apple-skin, very little was known of the changes produced in cider during the mysterious process of “working.” Now, when we see the bubbles of gas in the glass of cider we know what has produced them, and we know too that a poison which we do not see is there also in corresponding amounts. We have learned, too, to trace the wrecked hopes of many a farmer’s family to the alcohol in the cider which he provided so freely, supposing it harmless.

Beer and other malt liquors are made from grain. By sprouting the grain, which changes its starch to sugar, and then dissolving out the sugar with water, a sweet liquid is obtained which is fermented with yeast, one kind of alcoholic ferment. Some kinds of beer contain only a small percentage of alcohol, but these are usually drunk in proportionately large amounts. The life insurance company finds the beer drinker a precarious risk; the surgeon finds him an unpromising subject; the criminal court finds him conspicuous in its proceedings. The united testimony from all these sources is that beer is demoralizing, mentally, morally, and physically.

127. Cooking. The process through which nearly all food used by civilized man has to pass before it is eaten is known as cooking. Very few articles indeed are consumed in their natural state, the exceptions being eggs, milk, oysters, fruit and a few vegetables. Man is the only animal that cooks his food. Although there are savage races that have no knowledge of cooking, civilized man invariably cooks most of his food. It seems to be true that as nations advance in civilization they make a proportionate advance in the art of cooking.

Cooking answers most important purposes in connection with our food, especially from its influence upon health. It enables food to be more readily chewed, and more easily digested. Thus, a piece of meat when raw is tough and tenacious, but if cooked the fibers lose much of their toughness, while the connective tissues are changed into a soft and jelly-like mass. Besides, the meat is much more readily masticated and acted upon by the digestive fluids. So cooking makes vegetables and grains softer, loosens their structure, and enables the digestive juices readily to penetrate their substance.

Cooking also improves or develops flavors in food, especially in animal foods, and thus makes them attractive and pleasant to the palate. The appearance of uncooked meat, for example, is repulsive to our taste, but by the process of cooking, agreeable flavors are developed which stimulate the appetite and the flow of digestive fluids.

Another important use of cooking is that it kills any minute parasites or germs in the raw food. The safeguard of cooking thus effectually removes some important causes of disease. The warmth that cooking imparts to food is a matter of no slight importance; for warm food is more readily digested, and therefore nourishes the body more quickly.

The art of cooking plays a very important part in the matter of health, and thus of comfort and happiness. Badly cooked and ill-assorted foods are often the cause of serious disorders. Mere cooking is not enough, but good cooking is essential.


Experiments with the Proteids.

Experiment 31. As a type of the group of proteids we take the white of egg, egg-white or egg-albumen. Break an egg carefully, so as not to mix the white with the yolk. Drop about half a teaspoonful of the raw white of egg into half a pint of distilled water. Beat the mixture vigorously with a glass rod until it froths freely. Filter through several folds of muslin until a fairly clear solution is obtained.

Experiment 32. To a small quantity of this solution in a test tube add strong nitric acid, and boil. Note the formation of a white precipitate, which turns yellow. After cooling, add ammonia, and note that the precipitate becomes orange.

Experiment 33. Add to the solution of egg-albumen, excess of strong solution of caustic soda (or potash), and then a drop or two of very dilute solution (one per cent) of copper sulphate. A violet color is obtained which deepens on boiling.

Experiment 34. Boil a small portion of the albumen solution in a test tube, adding drop by drop dilute acetic acid (two per cent) until a flaky coagulum of insoluble albumen separates.

Experiments with Starch.

Experiment 35. Wash a potato and peel it. Grate it on a nutmeg grater into a tall cylindrical glass full of water. Allow the suspended particles to subside, and after a time note the deposit. The lowest layer consists of a white powder, or starch, and above it lie coarser fragments of cellulose and other matters.

Experiment 36. Examine under the microscope a bit of the above white deposit. Note that each starch granule shows an eccentric hilum with concentric markings. Add a few drops of very dilute solution of iodine. Each granule becomes blue, while the markings become more distinct.

Experiment 37. Examine a few of the many varieties of other kinds of starch granules, as in rice, arrowroot, etc. Press some dry starch powder between the thumb and forefinger, and note the peculiar crepitation.

Experiment 38. Rub a few bits of starch in a little cold water. Put a little of the mixture in a large test tube, and then fill with boiling water. Boil until an imperfect opalescent solution is obtained.

Experiment 39. Add powdered dry starch to cold water. It is insoluble. Filter and test the filtrate with iodine. It gives no blue color.

Experiment 40. Boil a little starch with water; if there is enough starch it sets on cooling and a paste results.

Experiment 41. Moisten some flour with water until it forms a tough, tenacious dough; tie it in a piece of cotton cloth, and knead it in a vessel containing water until all the starch is separated. There remains on the cloth a grayish white, sticky, elastic “gluten,” made up of albumen, some of the ash, and fats. Draw out some of the gluten into threads, and observe its tenacious character.

Experiment 42. Shake up a little flour with ether in a test tube, with a tight-fitting cork. Allow the mixture to stand for an hour, shaking it from time to time. Filter off the ether, and place some of it on a perfectly clean watch glass. Allow the ether to evaporate, when a greasy stain will be left, thus showing the presence of fats in the flour.

Experiment 43. Secure a specimen of the various kinds of flour, and meal, peas, beans, rice, tapioca, potato, etc. Boil a small quantity of each in a test tube for some minutes. Put a bit of each thus cooked on a white plate, and pour on it two or three drops of the tincture of iodine. Note the various changes of color,–blue, greenish, orange, or yellowish.

Experiments with Milk.

Experiment 44. Use fresh cow’s milk. Examine the naked-eye character of the milk. Test its reaction with litmus paper. It is usually neutral or slightly alkaline.

Experiment 45. Examine with the microscope a drop of milk, noting numerous small, highly refractive oil globules floating in a fluid.

Experiment 46. Dilute one ounce of milk with ten times its volume of water. Add cautiously dilute acetic acid until there is a copious, granular-looking precipitate of the chief proteid of milk (caseinogen), formerly regarded as a derived albumen. This action is hastened by heating.

Experiment 47. Saturate milk with Epsom salts, or common salt. The proteid and fat separate, rise to the surface, and leave a clear fluid beneath.

Experiment 48. Place some milk in a basin; heat it to about 100° F., and add a few drops of acetic acid. The mass curdles and separates into a solid curd (proteid and fat) and a clear fluid (the whey), which contains the lactose.

Experiment 49. Take one or two teaspoonfuls of fresh milk in a test tube; heat it, and add a small quantity of extract of rennet. Note that the whole mass curdles in a few minutes, so that the tube can be inverted without the curd falling out. Soon the curd shrinks, and squeezes out a clear, slightly yellowish fluid, the whey.

Experiment 50. Boil the milk as before, and allow it to cool; then add rennet. No coagulation will probably take place. It is more difficult to coagulate boiled milk with rennet than unboiled milk.

Experiment 51. Test fresh milk with red litmus paper; it should turn the paper pale blue, showing that it is slightly alkaline. Place aside for a day or two, and then test with blue litmus paper; it will be found to be acid. This is due to the fact that lactose undergoes the lactic acid fermentation. The lactose is converted into lactic acid by means of a special ferment.

Experiment 52. Evaporate a small quantity of milk to dryness in an open dish. After the dry residue is obtained, continue to apply heat; observe that it chars and gives off pungent gases. Raise the temperature until it is red hot; allow the dish then to cool; a fine white ash will be left behind. This represents the _inorganic matter_ of the milk.

Experiments with the Sugars.

Experiment 53. Cane sugar is familiar as cooking and table sugar. The little white grains found with raisins are grape sugar, or glucose. Milk sugar is readily obtained of the druggist. Prepare a solution of the various sugars by dissolving a small quantity of each in water. Heat each solution with sulphuric acid, and it is seen to darken or char slowly.

Experiment 54. Place some Fehling solution (which can be readily obtained at the drug store as a solution, or tablets may be bought which answer the same purpose) in a test tube, and boil. If no yellow discoloration takes place, it is in good condition. Add a few drops of the grape sugar solution and boil, when the mixture suddenly turns to an opaque yellow or red color.

Experiment 55. Repeat same experiment with milk sugar.

Chapter VI.


128. The Purpose of Digestion. As we have learned, our bodies are subject to continual waste, due both to the wear and tear of their substance, and to the consumption of material for the production of their heat and energy. The waste occurs in no one part alone, but in all the tissues.

Now, the blood comes into direct contact with every one of these tissues. The ultimate cells which form the tissues are constantly being bathed by the myriads of minute blood-vessels which bring to the cells the raw material needed for their continued renewal. These cells are able to select from the nutritive fluid whatever they require to repair their waste, and to provide for their renewed activity. At the same time, the blood, as it bathes the tissues, sweeps into its current and bears away the products of waste.

Thus the waste occurs in the tissues and the means of repair are obtained from the blood. The blood is thus continually being impoverished by having its nourishment drained away. How, then, is the efficiency of the blood maintained? The answer is that while the ultimate purpose of the food is for the repair of the waste, its immediate destination is the blood.[19]

129. Absorption of Food by the Blood. How does the food pass from the cavity of the stomach and intestinal canal into the blood-vessels? There are no visible openings which permit communication. It is done by what in physics is known as _endosmotic_ and _exosmotic_ action. That is, whenever there are two solutions of different densities, separated only by an animal membrane, an interchange will take place between them through the membrane.

To illustrate: in the walls of the stomach and intestines there is a network of minute vessels filled with blood,–a liquid containing many substances in solution. The stomach and intestinal canal also contain liquid food, holding many substances in solution. A membrane, made up of the extremely thin walls of the blood-vessels and intestines, separates the liquids. An exchange takes place between the blood and the contents of the stomach and bowels, by which the dissolved substances of food pass through the separating membranes into the blood.

[Illustration: Fig. 46.–Cavities of the Mouth, Pharynx, etc. (Section in the middle line designed to show the mouth in its relations to the nasal fossæ, the pharynx, and the larynx.)

A, sphenoidal sinus;
B, internal orifice of Eustachian tube; C, velum palati;
D, anterior pillar of soft palate; E, posterior pillar of soft palate;
F, tonsil;
H, lingual portion of the pharynx; K, lower portion of the pharynx;
L, larynx;
M, section of hyoid bone;
N, epiglottis;
O, palatine arch

This change, by which food is made ready to pass into the blood, constitutes food-digestion, and the organs concerned in bringing about this change in the food are the digestive organs.

130. The General Plan of Digestion. It is evident that the digestive organs will be simple or complex, according to the amount of change which is necessary to prepare the food to be taken up by the blood. If the requisite change is slight, the digestive organs will be few, and their structure simple. But if the food is varied and complex in composition, the digestive apparatus will be complex. This condition applies to the food and the digestion of man.

[Illustration: Fig. 47.–Diagram of the Structure of Secreting Glands.

A, simple tubular gland;
B, gland with mouth shut and sac formed; C, gland with a coiled tube;
D, plan of part of a racemose gland ]

The digestive apparatus of the human body consists of the alimentary canal and tributary organs which, although outside of this canal, communicate with it by ducts. The alimentary canal consists of the mouth, the pharynx, the œsophagus, the stomach, and the intestines. Other digestive organs which are tributary to this canal, and discharge their secretions into it, are the salivary glands,[20] the liver, and the pancreas.

The digestive process is subdivided into three steps, which take place in the mouth, in the stomach, and in the intestines.

131. The Mouth. The mouth is the cavity formed by the lips, the cheeks, the palate, and the tongue. Its bony roof is made up of the upper jawbone on each side, and the palate bones behind. This is the _hard palate_, and forms only the front portion of the roof. The continuation of the roof is called the _soft palate_, and is made up of muscular tissue covered with mucous membrane.

The mouth continues behind into the throat, the separation between the two