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THE FRAMEWORK OF THE HOUSE WE LIVE IN. 19

TOUCH.

The sense of touch has a large number of nerves in all parts of the body, continually carrying messages to the brain. These nerves are not, as might be supposed, on the surface of the skin. The body has in reality two skins, an outer and an inner skin. The outer skin merely serves as a covering to the real skin which lies underneath; and in this the nerves of touch are placed. Were it not for this outer skin, we would always be in pain, for the delicate nerves of touch could not even bear coming in contact with the air.

In the tips of the fingers the outer skin is very thin; and therefore the sense of touch in that part of the hand is extremely delicate.

No animals have such perfect instruments of touch as the fingers of the human hand. In the hoof of the horse, or the paw of the dog, there is no delicate sense of touch. Animals have their sense of touch mostly in their lips and tongues. The elephant has this sense chiefly in the finger-shaped end of his trunk. In the cat, the whiskers act as feelers, there being delicate nerves of touch at the root of each of the long hairs. Some insects have feelers extending from their heads, and we often see them touching things with their feelers as we do with our hands.

8.-THE FRAMEWORK OF THE HOUSE
WE LIVE IN.

THE bones are the framework of the house we live in. They are to the body what timbers are to a building.

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THE FRAMEWORK OF THE HOUSE WE LIVE IN.

Those of the lower extremities may be called the pillars of the house. They are commonly reckoned in three divisions: the thigh, the leg, and the foot.

The thigh is the longest bone in the human body. Its lower part is joined to the bone of the leg, and where the two meet they form what is called a hinge joint; which means a joint that will only allow of motion backwards and forwards in one direction, like a door on hinges.

The foot consists of twenty-six little bones, so bound together by strong, tough ligaments, as to form an arch. When we walk or run, this arch yields like a spring to the surface on which we tread. If the foot consisted only of one solid bone, it would entirely want its spring or elasticity, and we would stump about with a heavy, hard sound, similar to that made by the hoof of a horse. In standing, we rest only on the heel and the fore part of the foot, the arch between forming a hollow which serves to lodge and protect the vessels and nerves that descend from the leg to the toes.

A chain or column of twenty-four bones, placed one above the other, form what is called the spine or backbone of the body. When we make a bow, there is a little motion between each two of the whole twenty-four bones; and this makes the motion easy and graceful. Were the spine all one bone, the movement of the body would be stiff and ungraceful. On the top of this column of bones rests the head, in which is placed the brain, the central abode of the soul. In the ivory palace of the skull are placed the four principal gateways of knowledge,-the eye, the ear, the nose, and the mouth.

A set of ribs, or bones like the hoops of a barrel, form the framework of the chest. There are twelve of these

THE FRAMEWORK OF THE HOUSE WE LIVE IN. 21

ribs on each side of the body, all joined at the back to the spine. Seven of them on each side are also joined in front to the breast-bone, which is about half the length of the spine. A strong gristly substance stretches down from each of the seventh ribs, and joins together the other five ribs.

The upper part of the arm consists of only one bone. The head of it is a smooth, round ball, which fits into a kind of cup in the shoulder-bone. This cup is called a socket, and the whole joint is termed a ball-and-socket joint. The ball turns in the socket, so that we can not only make the arm move backwards and forwards, but can give it also a whirling motion.

The joint at the elbow is of a different kind. It is like that of the knee, a hinge joint, and can only move backwards and forwards.

Below the elbow the arm consists of two bones, which roll on each other in such a way that the palm of the hand can be turned in different directions. At the wrist

the chief motion is a hinge motion.

The hand possesses a large number of bones; eight in the wrist, five in the palm, and fourteen in the fingers— each finger possessing three, except the thumb, which has only two.

The teeth do not grow like the other bones. When once fully formed, the passage of vessels and nerves to the teeth is almost closed; so that when a tooth is broken or decayed it does not possess the power of repairing itself. Still, however, its root, or fang, is penetrated by a small nerve; and it is to the action of the air on this nerve that the pain of toothache is chiefly due.

As the jaw-bone of a child enlarges, the teeth become

too small to fill it; and this is the reason that we have two sets of teeth. The first set begin to remove about the seventh year, and a new set take their place. The new teeth are not only larger, but more in number, and they fill up all the room designed for them in the enlarged jaws.

All the bones of our bodies are inside, and are covered with muscles, cords, and ligaments, and over all is the skin. But the bones of some animals are on the outside, as in the case of crabs and lobsters. Their bones make a kind of coat of mail, to protect the soft parts from being injured. Such animals have new skeletons every year. They crawl into a retired place, and gradually the shell comes apart, and the animal pulls himself out of it. Another case or skeleton is soon formed, and the animal comes forth again with his new armour on, as brave and ready to fight as ever.

9.-WHAT IS BONE MADE OF ?

BONE consists of both mineral and animal matter. By soaking a bone in muriatic acid all the earthy matter can be removed; and then the bone becomes soft and pliable. Again, by subjecting a bone to a strong heat the animal portion will be burnt out, and the earthy matter will remain; but the earthy particles adhere so slightly together that the least touch will break them. Thus we see that the hardness of bone is given by the earthy matter, while its tenacity, or toughness, depends on the animal portion. The bones of an old person have less animal matter, and therefore are more brittle, than those of the young.

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When we examine a section of a bone through a microscope, we find it traversed by a network of minute canals, through which nourishment is conveyed to the bone precisely as sap spreads to the different parts of a tree.

10. THE MUSCLES.

THE muscles are the fleshy part of the body. Besides giving roundness and beauty to the human form, they possess the power of shrinking and lengthening like a piece of India-rubber. Attached to them are strong white cords called sinews or tendons, the ends of which are fastened to the bones. When the muscles contract they pull these tendons, and thus give motion to the different parts of the body. For example, if I wish to bring my hand to my head, the muscles on my arm between the shoulder and the elbow immediately shrink and pull up the forearm. When I wish my hand to go back, another set of muscles on the back part of the arm contract, and straighten out the arm again. The muscles are usually thus found in pairs, one set to bend a limb, another to straighten it. The whole body contains about four hundred and fifty muscles, or two hundred and twenty-five pairs, the uses of which have been ascertained. By these muscles all the motions of the body are performed. The bones could not move without them, and any part unfurnished with suitable muscles would be motionless. The bones and the muscles are thus necessary to each other; and their union displays the wisdom and goodness of Him who is the maker and framer of our bodies.

There are about one hundred and fifty muscles concerned

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