60. Broken Bones. The bones, especially those of the upper limbs, are often fractured or broken. The _simple_ fracture is the most common form, the bone being broken in a single place with no opening through the skin. When properly adjusted, the bone heals rapidly. Sometimes bones are crushed into a number of fragments; this is a _comminuted_ fracture.

When, besides the break, there is an opening through the soft parts and surface of the body, we have a _compound_ fracture. This is a serious injury, and calls for the best surgical treatment.

A bone may be bent, or only partly broken, or split. This is called "a green-stick fracture," from its resemblance to a half-broken green stick.

This fracture is more common in the bones of children.

Fractures may be caused by direct violence, as when a bone is broken at a certain point by some powerful force, as a blow from a baseball bat or a fall from a horse. Again, a bone may be broken by indirect violence, as when a person being about to fall, throws out his hand to save himself.

The force of the fall on the hand often breaks the wrist, by which is meant the fracture of the lower end of the radius, often known as the "silver-fork fracture." This accident is common in winter from a fall or slip on the ice.

Sometimes bones are broken at a distance from the point of injury, as in a fracture of the ribs by violent compression of the chest; or fracture may occur from the vibration of a blow, as when a fall or blow upon the top of the head produces fracture of the bones at the base of the brain.[6]

61. Treatment for Broken Bones. When a bone is broken a surgeon is needed to set it, that is, to bring the broken parts into their natural position, and retain them by proper appliances. Nature throws out between and around the broken ends of bones a supply of repair material known as plastic lymph, which is changed to fibrous tissue, then to cartilage, and finally to bone. This material serves as a sort of cement to hold the fractured parts together. The excess of this at the point of union can be felt under the skin for some time after the bone is healed.

With old people a broken bone is often a serious matter, and may cripple them for life or prove fatal. A trifling fall, for instance, may cause a broken hip (popularly so called, though really a fracture of the neck of the femur), from the shock of which, and the subsequent pain and exhaustion, an aged person may die in a few weeks. In young people, however, the parts of a broken bone will knit together in three or four weeks after the fracture is reduced; while in adults, six or even more may be required for firm union. After a broken bone is strong enough to be used, it is fragile for some time; and great care must be taken, especially with children, that the injured parts may not be broken again before perfect union takes place.[7]

62. The Effect of Alcohol upon the Bones. While the growth of the bones occurs, of course, mainly during the earlier years of life, yet they do not attain their full maturity until about the twenty-fifth year; and it is stated that in persons devoted to intellectual pursuits, the skull grows even after that age. It is plainly necessary that during this period of bone growth the nutrition of the body should be of the best, that the bones may be built up from pure blood, and supplied with all the materials for a large and durable framework. Else the body will be feeble and stunted, and so through life fall short of its purpose.

If this bony foundation be then laid wrong, the defect can never be remedied. This condition is seen in young persons who have been underfed and overworked. But the use of alcoholic liquors produces a similar effect, hindering bone cell-growth and preventing full development.[8]

The appet.i.te is diminished, nutrition perverted and impaired, the stature stunted, and both bodily and mental powers are enfeebled.

63. Effect of Tobacco upon the Bones. Another narcotic, the destructive influence of which is wide and serious, is tobacco. Its pernicious influence, like that of alcohol, is peculiarly hurtful to the young, as the cell development during the years of growth is easily disturbed by noxious agents. The bone growth is by cells, and a powerful narcotic like tobacco r.e.t.a.r.ds cell-growth, and thus hinders the building up of the bodily frame. The formation of healthy bone demands good, nutritious blood, but if instead of this, the material furnished for the production of blood is poor in quality or loaded with poisonous narcotics, the body thus defrauded of its proper building material becomes undergrown and enfeebled.

Two unfavorable facts accompany this serious drawback: one is, that owing to the insidious nature of the smoky poison[9] (cigarettes are its worst form) the cause may often be unsuspected, and so go on, unchecked; and the other, that the progress of growth once interrupted, the gap can never be fully made up. Nature does her best to repair damages and to restore defects, but never goes backwards to remedy neglects.

Additional Experiments.

Experiment 11. Take a portion of the decalcified bone obtained from Experiment 4, and wash it thoroughly in water: in this it is insoluble.

Place it in a solution of carbonate of soda and wash it again. Boil it in water, and from it gelatine will be obtained.

Experiment 12. Dissolve in hydrochloric acid a small piece of the powdered bone-ash obtained from Experiment 3. Bubbles of carbon dioxid are given off, indicating the presence of a carbonate. Dilute the solution; add an excess of ammonia, and we find a white precipitate of the phosphate of lime and of magnesia.

Experiment 13. Filter the solution in the preceding experiment, and to the filtrate add oxalate of ammonia. The result is a white precipitate of the oxalate of lime, showing there is lime present, but not as a phosphate.

Experiment 14. To the solution of mineral matters obtained from Experiment 3, add acetate of soda until free acetic acid is present, recognized by the smell (like dilute vinegar); then add oxalate of ammonia. The result will be a copious white precipitate of lime salts.

Experiment 15. _To show how the cancellous structure of bone is able to support a great deal of weight_. Have the market-man saw out a cubic inch from the cancellous tissue of a fresh beef bone and place it on a table with its princ.i.p.al layers upright. Balance a heavy book upon it, and then gradually place upon it various articles and note how many pounds it will support before giving way.

Experiment 16. Repeat the last experiment, using a cube of the decalcified bone obtained from Experiment 4.

[NOTE. As the succeeding chapters are studied, additional experiments on bones and their relation to other parts of the body, will readily suggest themselves to the ingenious instructor or the thoughtful student. Such experiments may be utilized for review or other exercises.]

Review a.n.a.lysis: The Skeleton (206 bones).

/ / 1 Frontal, / / 2 Parietal, / I. Cranium | 2 Temporal, / (8 bones) | 1 Occipital, / 1 Sphenoid, | 1 Ethmoid.

| | / 2 Superior Maxillary, The Head | / 2 Malar, (28 bones). | / 2 Nasal, | II. Face | 2 Lachrymal Bones, | (14 bones) | 2 Palate Bones, | 2 Turbinated, | 1 Vomer, 1 Lower Maxillary.

/ Hammer, III. The Ear | Anvil, (6 bones) Stirrup.

/ / 7 Cervical Vertebrae.

/ / 12 Dorsal Vertebrae, / I. Spinal Column | 5 Lumbar Vertebrae, | (26 bones) Sacrum, | Coccyx.

The Trunk | (54 bones). | / 7 True Ribs, | II. The Ribs | 3 False Ribs, | (24 bones) 2 Floating Ribs.

| III. Sternum.

IV. Two Hip Bones.

V. Hyoid Bone.

/ / Scapula, / I. Upper Arm | Clavicle, | Humerus.

| The Upper Limbs | II. Forearm / Ulna, (64 bones). | Radius.

| | / 8 Carpal Bones, III. Hand | 5 Metacarpal Bones, 14 Phalanges.

/ I. Thigh Femur.

/ | / Patella, The Lower Limbs | II. Lower Leg | Tibia, (60 bones). | Fibula.

| | / 7 Tarsal Bones, III. Foot | 5 Metatarsal Bones, 14 Phalanges.

Chapter III.

The Muscles.

64. Motion in Animals. All motion of our bodies is produced by means of muscles. Not only the limbs are moved by them, but even the movements of the stomach and of the heart are controlled by muscles. Every part of the body which is capable of motion has its own special set of muscles.

Even when the higher animals are at rest it is possible to observe some kind of motion in them. Trees and stones never move unless acted upon by external force, while the infant and the tiniest insect can execute a great variety of movements. Even in the deepest sleep the beating of the heart and the motion of the chest never cease. In fact, the power to execute spontaneous movement is the most characteristic property of living animals.

65. Kinds of Muscles. Most of the bodily movements, such as affect the limbs and the body as a whole, are performed by muscles under our control. These muscles make up the red flesh or lean parts, which, together with the fat, clothe the bony framework, and give to it general form and proportion. We call these muscular tissues voluntary muscles, because they usually act under the control of the will.

The internal organs, as those of digestion, secretion, circulation, and respiration, perform their functions by means of muscular activity of another kind, that is, by that of muscles not under our control. This work goes on quite independently of the will, and during sleep. We call the instruments of this activity involuntary muscles. The voluntary muscles, from peculiarities revealed by the microscope, are also known as striped or striated muscles. The involuntary from their smooth, regular appearance under the microscope are called the unstriped or non-striated muscles.

The two kinds of muscles, then, are the red, voluntary, striated muscles, and the smooth, involuntary, non-striated muscles.

66. Structure of Voluntary Muscles. The main substance which clothes the bony framework of the body, and which forms about two-fifths of its weight, is the voluntary muscular tissue. These muscles do not cover and surround the bones in continuous sheets, but consist of separate bundles of flesh, varying in size and length, many of which are capable of independent movement.

Each muscle has its own set of blood-vessels, lymphatics, and nerves. It is the blood that gives the red color to the flesh. Blood-vessels and nerves on their way to other parts of the body, do not pa.s.s through the muscles, but between them. Each muscle is enveloped in its own sheath of connective tissue, known as the fascia. Muscles are not usually connected directly with bones, but by means of white, glistening cords called tendons.

[Ill.u.s.tration: Fig. 30.--Striated (voluntary) Muscular Fibers.

A, fiber serparating into disks; B, fibrillae (highly magnified); C, cross section of a disk ]

If a small piece of muscle be examined under a microscope it is found to be made up of bundles of fibers. Each fiber is enclosed within a delicate, transparent sheath, known as the sarcolemma. If one of these fibers be further examined under a microscope, it will be seen to consist of a great number of still more minute fibers called fibrillae. These fibers are also seen marked cross-wise with dark stripes, and can be separated at each stripe into disks. These cross markings account for the name _striped_ or _striated_ muscle.

The fibrillae, then, are bound together in a bundle to form a fiber, which is enveloped in its own sheath, the sarcolemma. These fibers, in turn, are further bound together to form larger bundles called fasciculi, and these, too, are enclosed in a sheath of connective tissue. The muscle itself is made up of a number of these fasciculi bound together by a denser layer of connective tissue.

Experiment 17. _To show the gross structure of muscle._ Take a small portion of a large muscle, as a strip of lean corned beef. Have it boiled until its fibers can be easily separated. Pick the bundles and fasciculi apart until the fibers are so fine as to be almost invisible to the naked eye. Continue the experiment with the help of a hand magnifying gla.s.s or a microscope.