*"Setting Up" Exercises.*-The splendid carriage of students from military schools shows what may be accomplished in securing erectness of form where proper attention is given to this matter. The military student gets his fine form partly through his exercises in handling arms, but mainly through his so-called "setting up" drill. As a suggestion to one desiring to improve the form of his body, a modification of the usual "setting up"

drill is here given:

1. Standing erect, with the heels together, the feet at an angle of 45, and hands at the sides, bring the arms to a horizontal position in front, little fingers touching and nails down. From this position raise the hands straight over the head, bringing the palms gradually together. Then with a backward sweeping movement, return the hands again to the sides. Repeat several times.

2. With the feet as in the above exercise, bring the hands and the arms to a level with the shoulders, palms down, elbows bent, middle fingers of the two hands touching, and the extended thumbs touching the chest. Keeping the palms down and the arms on a level with the shoulders, extend the hands as far sideward and backward as possible, returning each time to the first position. As the hands move out, inhale deeply (through the nose), and as they are brought back, exhale quickly (through the mouth). Repeat several times.

3. With the arms at the sides and the feet side by side and touching, bring the hands in a circular movement to a vertical position over the head, and lock the thumbs. Keeping the knees straight and the thumbs locked, bend forward, letting the hands touch the ground if possible, and then bring the body and hands again to the vertical position. Then by a backward sweeping movement, return the hands again to the sides. Repeat.

While these exercises may be practiced whenever convenient, it is best to set apart some special time each day for them, as on retiring at night or on rising in the morning.

*Hygienic Footwear.*-A necessary aid to erectness of position in standing and walking is a properly fitting shoe. Heels that are too high tilt the body unnaturally forward, and shoes that cause any kind of discomfort in walking lead to unnatural positions in order to protect the feet. Shoes should fit snugly, being neither too large nor too small. Many shoes, however, are unhygienically constructed, and no attempt should be made to wear them. Certainly is this true of styles that approach the "French heel" or the "toothpick toe" (Fig. 107). However, many styles of shoes are manufactured that are both hygienic and neat fitting. Rubber heels, on account of their elasticity, are to be preferred to those made of leather.

[Fig. 107]

Fig. 107-Heels and toes of unhygienic and of hygienic footwear.

*The Skeleton in Childhood and Old Age.*-Certain peculiarities are found to exist in the bones of children and of old people which call for special care of the skeleton during the first and last periods of life. The bones of children are soft, lacking mineral matter, and are liable to become bent For this reason, children who are encouraged to walk at too early an age may bend the thigh bones, causing the too familiar "bow-legs." These bones may also be bent by having children sit on benches and chairs which are too high for the feet to reach the floor, and which do not provide supports for the feet. Wholesome food, fresh air, sunlight, and exercise are also necessary to the proper development of the bones of children.

Where these natural conditions are lacking, as in the crowded districts of cities, children often suffer from a disease known as "rickets," on account of which their bones are unnaturally soft and easily bent.

On account of the acc.u.mulation of mineral matter, the bones of elderly people become brittle and are easily broken, and from lack of vigor of the bone cells they heal slowly after such injuries occur. This makes the breaking of a bone by an aged person a serious matter. Old people should, as far as possible, avoid liabilities to falls, such as going rapidly up and down stairs, or walking on icy sidewalks, and should use the utmost care in getting about. In old people also the cartilage between the bones softens, increasing the liability of getting misshaped. Special attention, therefore, should be given to erectness of form, and to such exercises as tend to preserve the natural shape of the body.

*Treatment of Fractures.*-A fractured bone always requires the aid of a surgeon, and no time should be lost in securing his services. In the meantime the patient should be put in a comfortable position, and the broken limb supported above the rest of the body. Though the breaking of a bone is not, as a rule, a serious mishap, it is necessary that the very best skill be employed in setting it. Any failure to bring the ends of the broken bone into their normal relations permanently deforms the limb and interferes with its use.

*Dislocations and Sprains.*-Dislocations, if they be of the larger joints, also require the aid of the surgeon in their reduction and sometimes in their subsequent treatment. Simple dislocations of the finger joints, however, may be reduced by pulling the parts until the bones can be slipped into position.

_A sprain_, which is an overstrained condition of the ligaments surrounding a joint, frequently requires very careful treatment. When the sprain is at all serious, a physician should be called. Because of the limited supply of blood to the ligaments, they are slow to heal, and the temptation to use the joint before it is fully recovered is always great.

Ma.s.sage(82) judiciously applied to a sprained joint, by bringing about a more rapid change in the blood and the lymph, is beneficial both in relieving the pain, and in hastening recovery.

*Summary.*-The skeleton, or framework of the body, is a structure which is movable as a whole and in most of its parts. It preserves the form of the body, protects important organs, and supplies the mechanical devices, or machines, upon which the muscles act in the production of motion. The skeleton is adapted to its purposes through the number and properties of the bones, and through the cartilage and connective tissue a.s.sociated with the bones. The places where the different bones connect one with another are known as joints, and most of these admit of motion. The preservation of the natural form of the skeleton is necessary, both for its proper action and for the health of the body.

*Exercises.*-1. State the main purpose of the skeleton. What is the necessity for so many bones in its construction?

2. How may the per cent of animal and of mineral matter in a bone be determined?

3. What properties are given the bones by the animal matter? What by the mineral matter?

4. Locate the bone cells. What is their special function?

5. State the plan by which nourishment is supplied to the bone cells in different parts of the bone.

6. Give the uses of the periosteum.

7. State the purpose of the Haversian ca.n.a.ls. Of the ca.n.a.liculi.

8. Give functions of the spinal column.

9. Name the different materials used in the construction of a joint and the purpose served by each.

10. Name four mechanical devices, or machines, found in the skeleton and state the purpose served by each.

11. Name one or more of the body machines not located in the skeleton.

12. Of what advantage is the peculiar shape of the lower jaw? Of the ribs?

Of the bones of the pelvic girdle?

13. State the importance of preserving the natural form of the skeleton.

How are unnatural curves produced in the spinal column?

14. How may slight deformities of the skeleton be corrected?

15. What different systems are employed in the body in the production of motion? What is the special function of each?

PRACTICAL WORK

To obtain clear ideas of the form and functions of the bones, a careful examination of a prepared and mounted skeleton is necessary. Many of the bones, however, may be located and their general form made out from the living body. Bones of the lower animals may also be studied to advantage.

*Experiments to show the Composition of Bone.*-1. Examine a slender bone, like that in a chicken's leg. Note that it resists bending and is difficult to break. Note also that it is elastic-that, when slightly bent, it will spring back.

2. Soak such a bone over night in a mixture of one part hydrochloric acid and four parts water. Then ascertain by bending, stretching, and twisting what properties the bone has lost. The acid has dissolved out the mineral matter.

3. Burn a small piece of bone in a clear gas flame, or on a bed of coals, until it ceases to blaze and turns a white color. Can the bone now be bent or twisted? What properties has it lost and what retained? What substance has been removed from the bone by burning?

*Observation on the Gross Structure of Bone.*-1. Procure a long, dry bone.

(One that has lain out in the field until it has bleached will answer the purpose excellently.) Test its hardness, strength, and stiffness. Saw it in two a third of the distance from one end, and saw the shorter piece in two lengthwise. Compare the structure at different places. Find rough elevations on the outside for the attachment of muscles, and small openings into the bone for the entrance of blood vessels and nerves. Make drawings to represent the sections.

2. Procure a fresh bone from the butcher shop. Note the difference between it and the dry bone. Examine the materials surrounding the sides and covering the ends of the bone. Saw through the enlarged portion at the end and examine the red marrow. Saw through the middle of the bone and observe the yellow marrow.

*To show the Minute Structure of the Bone.*-Prepare a section of bone for microscopic study as follows: With a jeweler's saw cut as thin a slice as possible. Place this upon a good-sized whetstone, not having too much grit, and keeping it wet rub it under the finger, or a piece of leather, until it is thin enough to let the light shine through. The section may then be washed and examined with the microscope. If the specimen is to be preserved for future study, it may be mounted in the usual way, but with _hard_ balsam. Prepare and study both transverse and longitudinal sections, making drawings. The sections should be prepared from bones that are thoroughly dry but which have not begun to decay.

*To show the Structure of a Joint.*-Procure from a butcher the joint of some small animal (hog or sheep). Cut it open and locate the cartilage, synovial membrane, and ligaments. Observe the shape and surface of the rubbing parts and the strength of the ligaments.

CHAPTER XV - THE MUSCULAR SYSTEM

As already stated, the skeleton, the nervous system, and the muscular system are concerned in the production of motion. The skeleton and the nervous system, however, serve other purposes in the body, while the muscular system is devoted exclusively to the production of motion. For this reason it is looked upon as the special _motor_ system. The muscular tissue is the most abundant of all the tissues, forming about 41 per cent of the weight of the body.

*Properties of Muscles.*-The ability of muscular tissue to produce motion depends primarily upon two properties-the property of irritability and the property of contractility. _Irritability_ is that property of a substance which enables it to respond to a stimulus, or to act when acted upon.

_Contractility_ is the property which enables the muscle when stimulated to draw up, thereby becoming shorter and thicker (a condition called contraction), and when the stimulation ceases, to return to its former condition (of relaxation). The property of contractility enables the muscles to produce motion. Irritability is a condition necessary to their control in the body.

*Kinds of Muscular Tissue.*-Three kinds of muscular tissue are found in the body. These are known as the _striated_, or striped, muscular tissue; the _non-striated_, or plain, muscular tissue; and the _muscular tissue of the heart_. These are made up of different kinds of muscle cells and act in different ways to cause motion. The striated muscular tissue far exceeds the others in amount and forms all those muscles that can be felt from the surface of the body. The non-striated muscle is found in the walls of the food ca.n.a.l, blood vessels, air pa.s.sages, and other tubes of the body; while the muscular tissue of the heart is confined entirely to that organ.