"Not in the World of Light alone, Where God has built His blazing throne, Nor yet alone on earth below, With belted seas that come and go, And endless isles of sunlit green Is all thy Maker's glory seen - Look in upon thy wondrous frame, Eternal wisdom still the same!"

I. Form, Structure, Etc., of the Bones

The Skeleton, or framework of the "House we live in," is composed of about 200 bones.

Uses And Forms of The Bones. - They have three principal uses: 1. To protect the delicate organs; 2. To serve as levers on which the muscles may act to produce motion; and 3. To preserve the shape of the body.

Bones differ in form according to the uses they sub serve. For convenience in walking, some are long; for strength and compactness, some are short and thick; for covering a cavity, some are flat; and for special purposes, some are irregular. The general form is such as to combine strength and lightness. For example, all the long bones of the limbs are round and hollow. Therefore giving with the same weight a greater strength, and also a larger surface for the attachment of the muscles.

The Composition of the Bones at maturity is about one part animal to two parts mineral matter. The proportion varies with the age. In youth it is nearly half and half, while in old age the mineral is greatly in excess. By soaking a bone in weak muriatic acid, an. Therefore dissolving the mineral matter, its shape will not change, but its stiffness will disappear, leaving a tough, gristly substance (cartilage) which can be bent like rubber.

If the bone be burned in the fire. Therefore consuming the animal matter, the shape will still be the same, but it will have lost its tenacity, and the beautiful, pure-white residue may be crumbled into powder with the fingers.

W. Therefore see that a bone receives hardness and rigidity from its mineral, and tenacity and elasticity from its animal matter.

The entire bone is at first composed of cartilage, which gradually ossifies or turns to bone. Certain portions near the joints are long delayed in this process, and by their elasticity assist in breaking the shock of a fall. while those of elderly people are liable to fracture, and do not quickly unite.

The Structure of The Bones - When a bone is sawed lengthwise, it is found to be a compact shell filled with a spongy substance This filling increases in quantity, and becomes more porous at the ends of the bone. Therefore giving greater size to form a strong joint, while the solid portion increases near the middle, where strength alone is needed. Each fiber of this bulky material diminishes the shock of a sudden blow, and also acts as a beam to brace the exterior wall. The recumbent position of the alligator protects him from falls, and therefore his bones contain very little spongy substance.

In the body, bones are not the dry, dead, blanched things they commonly seem to be, but are moist, living, pinkish structures, covered with a tough membrane, called the per-i-os'-te-um from which radiate tiny tubes. The lacune are arranged in circles around larger tubes, termed from their discoverer, Haversian canals, which serve as passages for the blood vessels that nourish the bone.

Growth of The Bones. - By means of this system of canals, the blood circulates as freely through the bones as through any part of the body, The whole structure is constantly but slowly changing, old material being taken out and new put in. A curious illustration is seen in the fact that if madder be mixed with the food of pigs, it will tinge their bones red.

Repair of The Bones. - When a bone is broken, the blood at once oozes out of the fractured ends. This soon gives place to a watery fluid, which in a fortnight thickens to a gristly substance, strong enough to hold them in place. Bone matter is then slowly deposited, which in five or six weeks will unite the broken parts. Nature, at first, apparently endeavors to remedy the weakness of the material by excess in the quantity, and so the new portion is larger than the old. But the extra matter will be gradually absorbed, sometimes so perfectly as to leave no trace of the injury.

A broken limb should be held in place by splints, or a plaster cast, to enable this process to go on uninterruptedly, and also lest a sudden jar might rupture the partially mended break. For a long time, the new portion consists largely of animal matter, and so is tender and pliable. The utmost care is therefore necessary to prevent a malformation.

The Joints are packed with a soft, smooth cartilage, or gristle, which fits so perfectly as to be airtight. Upon convex surfaces, it is thickest at the middle, and upon concave surfaces, it is thickest at the edge, or where the wear is greatest. In addition, the ends of the bones are covered with a thin membrane, the synovial (sun, with; ovum, an egg), which secretes a viscid fluid, not unlike the white of an egg. This lubricates the joints, and prevents the noise and wear of friction. The body is the only machine that oils itself.

The bones which form the joint are tied with stout ligaments (ligo, I bind), or bands, of a smooth, silvery white tissue, so strong that the bones are sometimes broken without injuring the fastenings.

Tags: Health