The Stiffening Rods Of The Body-machine


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Sources: A Handbook Of Health

What 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.



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 vertebrae. Each one of these vertebrae 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.





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.





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