A Handbook of Health by Woods Hutchinson (learn to read books .txt) 📖
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If these waste-materials form in the muscles faster than the blood can wash them out, they poison the muscle-cells and we begin to feel tired, or fatigued. This is why our muscle-cells are often so stiff and sore next morning after a long tramp, or a hard day's work, or a football game. A hot bath or a good rub-down takes the soreness out of the muscles by helping them to get these poisonous wastes out of their cells.
Thus when we play or run or work, we are not only exercising our muscles and making them gain strength and skill, but we are stirring up, or stimulating, almost every part of our body to more vigorous and healthful action.
Indeed, as our muscles alone, of all our body stuffs, are under the control of the will, our only means of deliberately improving our appetites, or strengthening our hearts or circulation, or invigorating our lungs, or causing a large part of our brains and minds to grow and develop, is through muscular exercise. This is why nature has taken care to make us all so exceedingly fond of play, games, and sports of all sorts, in the open air, when we are young; and, as we grow older, to enjoy working hard and fighting and "hustling," as we say; and that is the reason, also, why we are now making muscular exercise such an important part of education.
CHAPTER XIX THE STIFFENING RODS OF THE BODY-MACHINEWhat Bones Are. The bones are not the solid foundation and framework upon which the body is built, as they are usually described. They are simply a framework of rods and plates which "petrified," or turned into spongy limestone after the body was built, to make it firmer and stiffen it for movement. All the animals below the fishes, such as worms, sea-anemones, oysters, clams, and insects, get along very well without any bones at all; and when we are born, our bones, which haven't fully "set" yet, are still gristly and soft. The cores of the limbs, as they begin to stiffen, first turn into gristle, or cartilage, and later into bone; indeed, many of our bones remain gristle in parts until we are fifteen or sixteen years of age. This is why children's bones, being softer and more flexible than those of grown-up people, are not so liable to break or snap across when they fall or tumble about; and why, too, they are more easily warped or bent out of shape through lack of proper muscular exercise and proper food.
Bones are strips of soft body-stuff soaked with lime and hardened, like bricklayer's mortar, or concrete.[24] When you know the shape of the body, you know the bones; for they simply form a shell over the head and run like cores, or piths, down the centre of the back, and down each joint of the limbs.
In turning into spongy limestone, or animal concrete, they have become one of the deadest tissues in the body. They are tools of the muscles, the levers by which the muscles move the limbs and body about; they never do anything of their own accord. On account of their lifelessness and lack of vitality, they are rather easily attacked by disease, or broken by a blow or fall. There are such a large number of bones (two hundred and six, all told), and they resist decay and last so much longer after death than any other parts of the body, that they fill our museums and text-books of anatomy, form most of our fossils, and have thus given us rather an exaggerated idea of their importance during life.
The Frame-Work of the Body. Just look at any part of the body and imagine that it has a bony core of about the same general shape as itself, and you can reason out all the bones of the skeleton. To begin at the top, the skull is a box of strong, plate-like bones, which have hardened to protect the brain as it grew; and the shape of its upper, or brain, part is exactly that of the head, as you can easily feel by laying your hands upon it. Then come bony shells, or sockets, for the eyes and nose; and, below these, two heavy half-circles of bone, like the jaws of a steel trap, to carry the teeth.
V, vertebra; C, cartilage protecting spinal cord; A, point of articulation on the right side.
The thickness of the lower jaw and the size and squareness of the angle where it bends upward to be hinged to the skull, below the ear, are what give the appearance of squareness and determination to the faces of strong, vigorous men or women. If we want to imply that a person has a feeble will, or weak character, we say he has a "weak jaw."
The skull rests upon the top of the backbone, or spinal column, which, instead of being one long solid bone, is made up of a number of pieces, or sections, known as vertebræ. Each one of these vertebræ has a ring, or arch, upon its back. These, running one after the other, form a jointed, bony tube to protect the spinal cord, or main nerve-cable of the body, which runs through it.
Although the backbone can bend forward or backward, or twist from side to side a little, by the little pieces of bone of which it is built up gliding and turning upon one another, it is really very stiff and rigid, so as to protect the spinal cord and prevent its being stretched or pinched. Most of the movements which we call bending the spine are really movements of other joints which connect the body or head with it. When we bend our necks, for instance, we hardly bend the backbone at all, as most of the movement is made in the joint at the top of it, between it and the skull. Similarly, when we bend our backs, we really bend our backbones very little; for most of the movement comes at the hip joints, between the thighs and the hip bones.
Each of the limbs has a single, long, rounded bone in the upper part, known in the arm as the humerus, and two bones in the lower part. These last are known as the radius and ulna (the "funny bone") in the forearm, and the tibia and fibula in the leg. The shoulder-joint is made by the rounded head of the humerus fitting into the shallow cup of the scapula, or shoulder-blade. It is shallower than the hip joint to allow it freer movement; but this makes it weaker and much more easily dislocated, or put out of joint,—the most so, in fact, of any joint in the body.
Hip joint.
Knee joint, with the knee cap removed
The hip joints are deep, strong, cup-shaped sockets upon each side of the hip bones, or pelvis, into which fit the heads of the femurs or thigh bones. When the hip joint does become dislocated, it is very hard to put back again, on account of its depth and the heavy muscles surrounding it. It is quite subject to the attack of tuberculosis, or "hip-joint disease."
The joints, or points at which the bones join one another, look rather complicated, but they are really as simple as the bones themselves. Each joint has practically made itself by the two bones' rubbing against each other, until finally their ends became moulded to each other, and formed the ball-and-socket, or the hinge, according to whichever the movements of the "bend" required. The ends, or heads, of the bones which form a joint are covered with a smooth, shining coating of cartilage, or gristle, so that they glide easily over each other.
Around each joint has grown up a strong sheath of tough, fibrous tissue to hold the bones together; and, inside this, between the heads of the bones, is a very delicate little bag, or pouch, containing a few drops of smooth, slippery fluid (synovial fluid) to lubricate the movements of the joint. This is sometimes called the "joint oil," though it is not really oil.
Bones are covered with a tough skin, or membrane (periosteum). They are hardest and most solid on their surfaces, and hollow, or spongy, inside. The long bones of the limbs are hollow, and the cavity is filled with a delicate fat called marrow—just as an elderberry stem or willow-twig is filled with pith. This tubular shape makes them as strong as if they were solid, and much lighter.[25]
The short, square, and flattened bones of the body, such as those of the wrist, the skull, and the hips, instead of being hollow inside are spongy; and the spaces in the bone-sponge are filled with a soft tissue called the red marrow in which new red and white corpuscles for the blood are born, to take the place of those which die and go to pieces.
CHAPTER XX OUR TELEPHONE EXCHANGE AND ITS CABLESThe Brain. We are exceedingly proud of our brain and inclined to regard it as the most important part of our body. So it is, in a sense; for it is the part which, through its connecting wires, called the nerves, ties together all the widely separated organs and regions in our body, and helps them to work in harmony with one another. We speak of it as the master and controller of the body; but this is only partially true.
The brain is not so much the President of our Cell Republic as a great central telephone exchange, where messages from all over the body are received, sifted, and transmitted in more or less modified form, to other parts of the body. Three-fourths of the work of the brain consists in acting as "middle-man," or transmitter, of messages from one part of the body to another. In fact, the brain is far more the servant of the body than its ruler; and depends for its food supply, its protection, its health, and its very life, upon the rest of the body. The best way to keep the brain clear and vigorous is to keep the muscles of the stomach, the liver, the heart, and the entire body in good health.
What the Brain Does. The brain is the very wonderful organ with which we do what we are pleased to call our thinking, and also a number of other more important things of which we are not conscious at all. It is a large organ, weighing nearly three pounds when full grown. In shape it is like an oval loaf of bread split lengthwise by a great groove down the centre, and with a curiously wrinkled or folded surface. The two halves of the brain, called hemispheres (though more nearly the shape of a coffee-bean), are alike; and each one, by some curious twist, or freak, of nature, receives messages from, and controls, the opposite half of the body—the right half controlling the left side of the body, while the left half controls the right side of the body. Thus an injury or a hemorrhage on the left side of the brain will produce paralysis of the right side, which is the side on which a stroke of paralysis most commonly occurs.
All the nerve fibres in each half or hemisphere
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