THE KIDNEYS

EXAMINE the body of one of the animals that hang in a meat market and you will find two dark red organs fastened to the back

wall of the body. They are bean-shaped, and lie half buried in fat, one on each side of the backbone.

What are these organs? They are the kidneys. What

do they do? They take wastes out of the blood. Is their work important? Their work is as important as the work of any other organ of the body, for if they fail to do it the wastes will poison the body and cause

death. We could no more FIG. 41.

get along without kidneys

The kidneys and the bladder.

than we could get along without our digestive organs or our lungs.

How the kidneys remove the body wastes. A large blood vessel passes into each kidney and sends branches into every part of it. As the blood passes through the kidneys, the kidneys purify it by taking the wastes out of it, just as the lungs purify the blood by taking the carbon dioxid out of it. The wastes from the

kidneys are carried to the bladder by a duct from

each kidney.

Keeping the kidneys in health. The kidneys have to remove the body wastes, and are best cared for by caring for the whole body. There are, however, some things that should be avoided if possible. Among the things that are especially likely to injure the kidneys may be mentioned heavy lifting, exposure to cold and wet, indigestion, eating too much meat, and especially the drinking of alcohol, which is one of the most common causes of kidney trouble.

Questions: 1. Where are the kidneys found in the body? 2. What is their function? 3. Name some things that injure the kidneys. 4. What effect have alcoholic drinks on the kidneys?

Suggestions and topics for development: It is well to emphasize the unity of the body and the necessity of taking care of the general health for the sake of the parts. The Wonderful OneHoss Shay may be read to the class and the application of the poem to the human body made. In later life the kidneys and the heart are in very many cases the weak parts, and such habits of life ought early to be formed that these organs will be conserved as much as possible.

FIG. 42. Swimming is an invigorating way to take a bath. It is also one of the best forms of exercise, because it brings into play the muscles of all parts of the body. (After Sorolla's "The Swimmers," in the Metropolitan Museum of Art.)

THE living parts of the body are extremely delicate and tender, and if they were exposed to hurts, to drying, and to disease germs they could not live. We therefore have over the whole body a tough coat which protects the delicate living body parts. The inner part of this coat is alive, but the part which comes in contact with the outside world is dead and keeps falling away in dry scales.

The structure of the skin. The skin is composed of an outer layer called the epidermis and an inner layer called the dermis. The epidermis has no

blood vessels in it, but its inner part is alive and keeps growing to take the place of the outer part that is all the time dying and falling away. Everywhere in the skin are little sweat glands that pour out the sweat on the surface of the skin.

The skin a regulator of the body heat. The temperature of the healthy body, winter and sum

bair

mer, is about 98.6 degrees.

epidermis It remains the same be

cause the skin regulates the

dermis

sweat gland

FIG. 43. A section of the skin, highly magnified.

it does in two ways. When we are hot, the blood vessels in the skin open up and allow the blood to come to the outside of the body, where it can be cooled. When we are cold, the vessels in the skin close up and keep the blood in the warm inner parts of the body. Another way in which the skin regulates the heat is through the sweat glands. These assist

in cooling the body by pouring out water on the skin. If the sweat glands fail to work, the temperature of the body goes too high and we have fever.

Wet the hand and hold it up to the wind. Do you feel your hand being cooled as the water evaporates from it? Or pour alcohol or gasoline over the hand and allow it to dry off. Do you feel that your hand is being cooled? Suppose the air was so moist that the sweat could not evaporate from the skin. Would it cool the body to have the skin wet with sweat? On what kind of day do we suffer most from heat?

The hair. The hair grows from the epidermis, and like the outer layer of the epidermis the hair is dead. It contains no blood vessels, and there is no sense of feeling in it. The growth of the hair is at the root. The hair is composed of the same material as the outer layer of the skin.

Each hair stands in a little pocket of the epidermis that is folded down deep into the dermis. Opening into this small pocket are little glands that pour out oil around the root of the hair. Brush your hair thoroughly and it will become smooth and glossy from the oil that you work out from around the roots. Fine hairs are found all over the body, and the oil that comes from the glands at the roots of these hairs keeps the skin from becoming dry.

The care of the hair. In the care of the hair nothing is so important as thoroughly brushing it. This brings the blood into the scalp and spreads the oil along the hair. The hair should not be wet