THE MUSCLES Our muscles are wrapped around our bodies in a very interesting way. Besides being organs of motion, they give the body form. Except in disease they are of a deep red color. They make up the lean meat, or flesh, of animals. All the motions of the body are effected through our muscles. ‘They bind the bony frame together, and they cover nerves, bloodvessels, and cavities. The muscles of the heart, by extending and contracting, make it beat; and in the same way the muscles controlling the lungs make them expand to draw in air and contract to expel air. The muscles of the eyes move them as we wish, and those of the mouth, tongue, and throat, enable us to speak.
KINDS OF MUSCLES Some muscles, such as those of the heart and stomach, work without being told by the mind. They are called involuntary muscles. Other muscles, like those which move the organs of speech, and those which control the action of the legs and arms, do so only when they are told to by the mind. Such are called voluntary muscles. The voluntary muscles are most of them attached to the bones, and the involuntary to such organs as the heart, stomach and intestines.
COMPOSITION OF THE MUSCLES The voluntary muscles are made up of bundles of fibers, nicely wrapped in a peculiar membrane, or tissue. The smallest fibers are finer than the finest silk thread. These small bundles of fibers are again bound together to make larger bundles. If we pick to pieces a bit of cotton string, it will be found to be made up of a great number of little fibers. And if a piece of dried beef is soaked in water for an hour or two, and then it is picked to pieces with a pin, it will also prove to be composed of small fibers. Involuntary muscles are made up of flattened bands of fibers, or of long fibers of a pale color. Each fiber contains a nucleus, which is rod-shaped. This kind of muscle forms the muscular coat of the stomach and intestines. A considerable proportion, usually about three-fourths, of the total weight of muscle is water. The remaining one-fourth is composed of a lime-like substance called calcium phosphate and a strange substance called myosin. Myosin is also called muscle-plasma. Shortly after death animal bodies become very stiff.. This is caused by the myosin, which coagulates—that is, becomes solid and hard.
HOW MUSCLES WORK Muscles have the power of shortening and again lengthening themselves. They are elastic and pliable. If the arm is drawn up so as to touch the chin, the outside arm muscles are lengthened, and, at the same time, the inside ones are shortened. In this they are obeying the command of the brain, which has sent a message to them by the nerves. We find also that the muscles will jerk if irritated, as occurs when the flesh is pricked by a pin. We do not fully understand how the muscles are able to move so quickly and so wonderfully, so we say the movement results from a nerve stimulus. Muscles will contract suddenly and with force, as when we throw out our arms to defend ourselves, or they will move very gently, as when we do some delicate work with the fingers. When we walk a long distance we feel tired, and if we are not accustomed to walking we shall grow more or less stiff when we rest. This is because the muscles are required to do more than they are prepared to do, and because their cells are not built up as fast as they are worn out. The contortionist and the acrobat train their muscles to do most wonderful work. They can bend their bodies into strange and seemingly impossible positions, and it is all done by long practice in shortening and lengthening certain muscles as they will.<Callout type="important" title="Training Muscles">Regular exercise helps maintain muscle strength and flexibility.</Callout>
Fig. 11.—Cells Warp Form Muscle Fibers AND Liver TISSUE. b, liver cells; C, muscle cells (involuntary); D, muscle cells (voluntary); E, cells of heart muscle.
Fig. 12.—Showing THE MUSCLES OF THE BACK.
Key Takeaways
- Muscles are essential for movement and body form.
- Voluntary muscles control actions like speaking, while involuntary muscles manage internal functions.
- Muscle composition includes water, calcium phosphate, and myosin.
Practical Tips
- Regular exercise can help maintain muscle strength and flexibility, as seen in acrobats and contortionists.
- Understanding the types of muscles (voluntary vs. involuntary) can aid in recognizing how different body parts function.
- Proper hydration is crucial for muscle health, given that a significant portion of muscle weight is water.
Warnings & Risks
- Overexertion can lead to muscle fatigue and stiffness, especially if not accustomed to physical activity.
- Ignoring proper training methods can result in improper muscle use and potential injury.
Modern Application
While the techniques described in this chapter are rooted in early 20th-century understanding of human physiology, they still provide a foundational framework for modern survival preparedness. Understanding how muscles work is crucial for maintaining physical fitness during emergencies or prolonged periods without access to medical care.
Frequently Asked Questions
Q: What are the main differences between voluntary and involuntary muscles?
Voluntary muscles, like those in the arms and legs, can be controlled by our minds. Involuntary muscles, such as those in the heart and stomach, work automatically without conscious control.
Q: How does muscle composition affect their function?
Muscles are composed of water, calcium phosphate, and myosin. Water helps with flexibility, while calcium phosphate and myosin contribute to contraction and movement.
Q: Why is it important to understand the types of muscles in the context of survival preparedness?
Understanding muscle types can help in recognizing how different body parts function during emergencies. For example, knowing that involuntary muscles control internal functions can be crucial for maintaining health when external medical assistance is unavailable.