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dermis.

each hair there is an oil gland, which secretes an oil for the softening of the hair and the skin near it. Do you know what it is that causes goose flesh" and makes your hair “stand on end?

It is tiny muscles in the pockets from which hairs grow. The nails are plates of very tough

FIG. 281. A nail, a epidermis. Like the hair, they grow special form of the epiout of the dermis by the constant dermis, growing out of the formation of new cells. Do their outer ends have blood or nerves ? What causes their pink color? What are the roots of the nails? What is the use of the nails?

392. What is the work of the Skin? — We have already learned many of the uses of the skin (see $$ 383 and 390). It is a wonderful covering for the body, protecting the cells that are inside from injuries, and from the germs of disease which are in the air. The skin also contains the nerves which give us the sense of touch.

The skin' acts like a delicate instrument for controlling the temperature of the body. If we are warm, the blood rushes to the skin, and the sweat glands pour out an abundance of the perspiration. If the body becomes cold, the blood vessels near the skin become smaller, and less blood comes near the surface of the body. Thus the body loses less heat. In some forms of fever the temperature of the body is higher than it should be, yet we have chills. Why is this? The reason is that the blood vessels near the skin remain closed, and we have the same sensation as if we were in a cold room.

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393. What is the Value of Bathing ? Review § 183. Are not the dead skin, the material left by the evapora

tion of the perspiration, and the dust and smoke and bacteria which attach themselves to our bodies, reasons enough for bathing the skin often?

The best sort of bath for cleaning the skin is a hot bath, but it should be taken at night, if possible, especially in winter. If it is taken in the daytime, it should be followed by a cold shower bath, or a dash of cold water, so that we may not " catch " cold. In the morning, especially in cold weather, a cold bath is the best. The cold water gives the body a shock, and the blood is driven inward from the skin, by the closing of the blood vessels near the skin. But after a vigorous rubbing with a rough towel

, the “ reaction” comes, and the skin glows as the blood reënters it. A cold sponge bath is excellent, if one cannot endure the shock of plunging into a tub of cold water. It should be followed by vigorous rubbing with a rough towel.

394. Exercises. 1. Why must an earthworm come out of the ground in a heavy rain?

2. Trace the course of food to the stomach and of air to the lungs. Where do these paths cross?

3. What two cavities are separated by the diaphragm ? Is the diaphragm a muscle? What is its work?

4. What is the scientific reason why you should remain in bed when you have a bad cold?

5. Why does it not cause you pain to cut off a hair? Why does it hurt to pull one out ?.

6. Do you think that the body can preserve its heat best by having a great deal of blood in the skin, or by withdrawing blood from the skin? Why then is it not best to take a hot bath just before going out on a cold day?

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7. What do you think causes the color of hair ?

8. What skin structures form our finger prints? Why can they be used to identify a person?

9. Give the reasons why you should breathe through the nose, and not the mouth.

Summary. - Respiration brings oxygen to the cells, and takes away the carbon dioxide given off by the cells.

The lowest animals respire through the cell wall or through the skin.

Water animals breathe through gills, by which dissolved oxygen is taken out of the water. Land animals have lungs, consisting of spongy tissue full of air tubes and air cells, as well as blood capillaries.

The air passages are the nasal passages, throat, larynx, windpipe, and bronchial tubes.

The vocal cords are in the larynx. In speaking and singing we use the throat, teeth, lips, and nose, as well as the vocal cords.

Colds, tobacco, alcohol, and tight clothing are likely to injure the air passages or lungs.

The skin consists of the epidermis, dermis, and fat. Out of the dermis grow hair and nails. It has oil glands and sweat glands, as well as the nerves of touch.

Bathing removes dead skin, waste material brought out by the perspiration, dust, and bacteria.

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CHAPTER XXXIX

SENSES AND HABITS

395. How Can Our Organs Work Together ? — Is our body like a clock, made up of many interesting parts, and needing only to be wound up from time to time to keep it going? Or is it more like an automobile, which needs constant adjustment of gasoline, air supply, steering gear, brakes, lubricators, and spark plugs, in order that it may run properly? You will agree that it is more like the automobile. But will the automobile run itself ? Must there not be a driver in control to make all the adjustments as they are needed? Does the body have a driver, or expert, in control of its delicate mechanism? Of course it does: the mind. So the automobile needs a driver, but the driver needs a mind. We cannot tell just where the mind is; we know only the organs through which it acts. We ordinarily call the brain the organ of the mind. There is a sense in which not merely the brain, but the whole system through which each part of the body knows when to begin acting, and when to stop, is the organ of the mind. This system is called the nerve system, or nervous system.

What cells of the body are the messengers which tell the mind what is needed by the body, and then carry the proper order back to the body? There is a special kind of cells for this purpose; they

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are called nerve cells (Fig. 282). Do these need to travel to the mind with their message, as the red corpuscles must travel to the cells with oxygen? No, there is a chain of cells, and the message leaps

-Cell Body from one link to the

Nerve Fiber next, until it is received by that organ

Fig. 282. of the nervous system looking like an ameba, is the cell body; the long,

A nerve cell. The enlarged part, which is able to send

slender part is the nerve fiber. back the answer.

A nerve cell consists of an enlarged portion, called the cell body, and a long, slender portion, which is called the nerve fiber. The outside of the cell body is usually gray, and the outside of the fiber, white. What we call a nerve is a bundle of the long, slender nerve fibers belonging to several nerve cells.

396. What is the work of the Brain ? - Suppose you go to a bank employing a large number of men, to make a request or to ask for information; will you go directly to the office of the president? Not if the bank is properly organized. You will be met at the door by the doorkeeper or a messenger, and he may be able to answer your question, or to grant your request, without your having to ask anyone else. But he may be obliged to ask a clerk, and the clerk may have to ask the chief clerk, and the chief clerk may need to go to the cashier or vicepresident. Possibly he may need to send you to the president himself. Why does the business have such an

. organization? Is it not because those who are at the head of the business need their time for their special work, and if they were consulted about everything that was brought to the bank, they would have no time left

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