A quart of milk contains more food for the body than a half pound of good beefsteak. A pint of milk will supply the body with about as much food as a pint of oysters. A bowl of milk and a half loaf of bread is a healthful supper for a boy or girl. Skim milk and b.u.t.termilk are healthful drinks which furnish much food for building bone, blood, and muscle.

[Ill.u.s.tration: FIG. 21.--Germs which grow in milk and make it sour.]

=When Milk is a Poison.=--In New York, Cincinnati, and Chicago it has been noticed for many years that large numbers of babies become sick in warm weather and many of them die. The doctors learned that most of the babies taken sick were being fed on cows' milk because their own mothers did not have enough for them. It was then found that the sick babies had been using milk from dairies where the stables were dirty, the cows soiled, and the hands of the milkers unclean. On this account much dirt got into the milk.

Babies fed on clean milk from clean cows kept in clean stables remained strong and well. By much study the doctors learned that _dirty milk is poisonous milk_. The poison is made by the germs or bacteria living by the millions in unclean stables and in milk buckets not well washed in boiling water. Dirty milk becomes most poisonous in hot weather because warmth makes the germs grow very fast and become so numerous that millions are present in a teaspoonful of milk.

=Keeping Milk Clean.=--During one week of hot weather in Cincinnati, over a hundred babies were poisoned with dirty milk. In the same week twice this number were made sick by unclean milk in Philadelphia.

During the hot part of the year in our country bad milk kills more than a half dozen babies every hour of the day and night.

The only way _to have milk clean is to have clean stables with clean cows, milked by clean hands, and the milk handled in clean pails, cans, and bottles which have been scalded after being washed_. The milk must then be kept cold until used, so that the germs will not grow in it.

=Saving the Baby from Bad Milk.=--If possible, milk should be bought for the baby in bottles sealed with a pasteboard lid. If milk turns sour the same day it is delivered, it is not fit for the baby to take.

Heating it makes most milk safer for use. The heating of milk to kill most of the germs is _pasteurizing_ it. It should be kept very hot for about fifteen minutes, but should not be allowed to boil. It should be cooled by placing the vessel on ice or in cold water.

The baby's bottle and nipple should be washed in cold water and then well scalded immediately after being used. The bottle, the nipple, and the milk should be kept away from flies and dust. One fly has been known to carry on its body more germs than there are leaves on a large tree.

[Ill.u.s.tration: FIG. 22.--Plan of the prison at Easton, Pa. The crosses show into which cells the flies brought typhoid germs from the sewer and made the prisoners sick with fever.]

=Flies and Fever in a Prison.=--In August, 1908, thirteen prisoners in the jail at Easton, Pennsylvania, were taken ill with typhoid fever.

They had not been near any sick persons and their food and water were found to be pure. All those sick were in cells in one end of the prison. About twenty feet from this end a sewer had been uncovered two weeks before and left open. This sewer carried the waste from the hospital where several patients were sick with the fever. Flies fed on the waste in the sewer and then with the germs sticking to their feet flew into the cells of the prisoners and walked over their cups, spoons, and food. A little girl who played near this open sewer and shared her lunch with the flies had a severe attack of fever two weeks later because the germs sc.r.a.ped from the flies' feet on her food got into her body and grew.

=Milk and Disease.=--We must be very careful to get not only clean milk but milk from healthy cows milked by persons who have no typhoid fever, scarlet fever, or diphtheria in their homes. If only one or two disease germs get into the milk from the hands of those who have nursed the sick, these will grow into immense numbers in a single day.

Many of those who use the milk will then become ill. Hundreds are made sick in this way every year.

PRACTICAL QUESTIONS

1. Why is milk a good food?

2. What does a gallon of milk contain?

3. What is cream?

4. How is b.u.t.ter made?

5. For whom is milk specially good?

6. How does milk become poisonous?

7. Why is dirty milk more poisonous in hot weather?

8. Tell what harm unclean milk does.

9. How may milk be kept clean?

10. Explain how milk is heated to make it safe for use.

11. Show how flies may cause fever.

12. Tell how milk may carry diphtheria into our homes.

CHAPTER VII

HOW THE BODY USES FOOD

=Organs for making ready the Food.=--Before the food can get into the blood and be carried over the body to feed the muscles and the brain, it must be made into a fluid. This changing of the solid food into a liquid by the stomach and other organs is called _digestion_. The organs which do this work are known as _digestive organs_. They consist of a _food tube_ and several bodies called _glands_.

=The Food Tube.=--The food ca.n.a.l is about thirty feet long. Its first part, the _mouth_, opens back of the tongue into the throat, named the _pharynx_. This leads into a tube, the gullet, pa.s.sing down through the back part of the chest into the _stomach_ below the diaphragm. The stomach is a bent sac opening into a tube over twenty-five feet long called the _bowels_ or _intestines_. This tube is folded into a bunch which fills a large part of the cavity of the abdomen.

[Ill.u.s.tration: FIG. 23.--The plan of a gland. _a_ carries blood to the gland and _v_ takes it away after the gland has taken out what it needs. On the right side the top of the gland has been cut off.]

=The Glands or Juice Makers.=--A gland is a little tube closed at one end, or a bunch of such tubes, which can take something out of the blood and make it into a juice. A gland under each ear and four others near the tongue make the juice called _saliva_ which flows into the mouth through tubes.

A long, flat, pink gland back of the stomach is called the _sweetbread_ or _pancreas_. This and a large brown gland, the _liver_, empty their juices into the intestines. The whole inner surface of the stomach and intestines is lined with tiny tubes, the glands. The juice of these with that of the other glands softens the food and makes it into a liquid.

=The Work of the Mouth.=--The mouth has three things to do: It should break the lumps of food into fine bits so it can be well wet with the slippery fluid called _saliva_ and also easily swallowed. It must roll the food about so that it gets soaked with saliva. It must hold the food long enough to get much taste from it because this starts the juices to flowing into the stomach. Food gives out its taste only after it is changed to a liquid. It should not be washed down with water, as this weakens the juices in the stomach.

[Ill.u.s.tration: FIG. 24.--The three glands which make the saliva for acting on the food in the mouth.]

No food should be swallowed until it is broken into bits nearly as small as the head of a pin. Some foods, such as cheese, bananas, and nuts, should be made even finer than this. There is nothing in the stomach to crush to pieces large lumps of food. The juices of the stomach can do their full work only when the food is well chewed in the mouth.

[Ill.u.s.tration: FIG. 25.--Photograph of a chestnut chewed a half minute by a boy who had poor teeth because he had not taken care of them. The lumps are so large that the juices of the stomach could not dissolve them.]

=The Chewing of Food keeps away Sickness.=--Bread, meat, and potatoes should be cut into pieces no larger than half the size of your thumb and each piece put separately into your mouth with a fork. It should then be chewed from twenty to thirty times before another piece is put into the mouth. Food treated in this way will not cause headache or a sickness in the stomach called _indigestion_ or _dyspepsia_. It is said that there are so many persons with this kind of sickness that more than $5,000,000 are spent every year for medicine to help them.

Too little chewing of the food while you are young may not cause many aches or pains, but if you form the habit of rapid eating it is hard to learn to eat slowly. No one who chews his food poorly can avoid sickness long or grow well and strong.

[Ill.u.s.tration: FIG. 26.--Photograph of a chestnut chewed a half minute by a boy with good teeth.]

=The Work of the Stomach.=--When the food is swallowed, it pa.s.ses through the gullet into the stomach. This is a sac holding more than a quart (Fig. 27). It is made of an outer wall of muscle and an inner skinlike coat full of tiny tubes called _gastric glands_. Millions of these give out drop by drop a watery fluid named _gastric juice_. This juice begins to flow as soon as we smell or taste food and continues to drop out as long as there is any food in the stomach.

The use of the gastric juice is to help change part of the food into a more watery fluid. To do this it must be well mixed with the food.

This mixing is done by the muscles in the outer wall of the stomach (Fig. 29). They squeeze together and then loosen up in such a way as to move the food about and turn it over until every particle is wet again and again with the gastric juice.

=How long Food stays in the Stomach.=--A ring of muscle around the end of the stomach keeps the food from escaping until it has become a thin grayish liquid. The stomach can finish its work on some kinds of food in one or two hours. With other foods it must work four or five hours.

The stomach can finish its work on soft boiled eggs, milk, roasted potatoes, and broiled lamb within two hours. With pork, veal, cabbage, and fried potatoes it must work four or five hours. When a person is sick the stomach is weak, and he should have only the food which causes the stomach the least work.

=The Work of the Intestines.=--The last part of the work in getting the food ready for the blood is done in the long folded tube known as the intestine (Fig. 27). Here juices coming from the pancreas and liver mix with the food and change into a liquid those parts not acted on in the stomach.

The intestine does quite as much work as the stomach. Sometimes when the stomach is sick, too much work is put off on the intestines and then they become sick and give much pain.

The pint of watery fluid from the pancreas and the quart of greenish yellow fluid called _bile_ given out by the liver are carried through two tubes into the intestine (Fig. 27). To mix these juices with the food the intestine is being swung gently back and forth and the walls squeezed together by muscles forming its outer coat. As soon as the intestine has finished its work the food begins to enter the blood.