Applied Physiology Part 2

_Second_, two sets of cells behind the stomach make two liquids and pour them into the intestine. One set of cells is the _sweetbread_, or _pancreas_, and its liquid is the _pancreatic juice_. The other is the _liver_ and its fluid is the _bile_.

_Third_, the pancreatic juice makes three changes in food. _First_, like the mouth, it changes starch to sugar. _Second_, like the stomach, it makes alb.u.min a liquid. _Third_, it divides fat into fine drops. These drops then mix with water and do not float on its top.

=20. Bile.=--The bile is yellow and bitter. It helps the pancreatic juice do its work. It also helps to keep the inside of the intestine clean.

=21. Digestion of water and minerals.=--Water and the mineral parts of food do not need to be changed at all, but can become part of the blood just as they are. Seeds and husks and tough strings of flesh all pa.s.s the length of the intestine and are not changed.

=22. How food gets into the blood.=--By the time food is half way down the intestine it is mostly liquid and ready to become part of the blood. This liquid soaks through the sides of the intestine and into the blood tubes. At last the food reaches the end of the intestine.

Most of its liquid has then soaked into the blood tubes and only some solid waste is left.

=23. Work of the liver.=--The food is now in the blood, but has not become a part of it. It is carried to the liver. There the liver changes the food to good blood, and then the blood hurries on and feeds the cells of the body. Spoiled food may be swallowed and taken into the blood with the good food. The liver takes out the poisons and sends them back again with the bile. The liver keeps us from getting poisoned.

=24. Bad food.=--Sometimes the stomach and intestine cannot digest the food. They cannot digest green apples, but they try hard to do so.

They stir the apples faster and faster until there is a great pain.

Sometimes the stomach throws up the food and then the pain and sickness stop. Spoiled food makes us sick in the same way.

=25. Too fast eating.=--When the food stays too long in the stomach or intestine it sours, or decays, just as it does outside of the body.

This makes us very sick. When we eat too much, or when we do not chew the food to small pieces, the stomach may be a long time in digesting the food. Then it may become sour and make us sick.

=26. Biliousness.=--When the food is poor or becomes sour, it is poorly digested. Then the liver has more work to do, and does not change the food to blood as it should. It also lets some of the sour poisons pa.s.s by it. These poison the whole body and make the head ache. We call this _biliousness_. The tongue is then covered with a white or yellow coat and the mouth tastes bad. These are signs of sickness. The stomach and liver are out of order.

=27. Rules for eating.=--If we eat as we should, our stomach will digest its food. We must follow three rules.

_First_, we must chew the food in the mouth until all the lumps are fine. Then the food will be ready for the stomach.

_Second_, we must eat slowly. If we eat fast we cannot chew the food well. The stomach cannot take care of food if it comes too fast. We must swallow all of one mouthful before we put another into the mouth.

_Third_, we must eat only at meal times. The stomach needs a rest.

Even a little candy, or apples, or nuts will keep the stomach at work, and tire it out. A child needs to eat more often than his father. So, besides his meals, he should have something to eat in the middle of the morning and some more in the afternoon. But he should not be eating at all hours. He ought not to eat little bits just before dinner, for that spoils his meal.

WHAT WE HAVE LEARNED

1. The stomach and intestine stir and rub the food, and mix it with juices.

2. The juices change alb.u.min to a liquid, and starch to sugar.

They also change fat to the form of tiny drops.

3. The digested food soaks through the sides of the intestine into the blood tubes.

4. The blood carries the food to the liver.

5. The liver changes food to blood.

6. Blood goes to all parts of the body and feeds the cells.

7. The liver keeps poisons from getting into the blood.

8. Water and minerals become a part of the blood without being digested.

9. When food is not well digested, the liver cannot make it into good blood. This makes us bilious.

10. If food is not soon digested it sours and decays. This makes us sick.

11. We can make food digest quickly by chewing it well and eating slowly.

CHAPTER V

FOODS

=28. Kinds of food.=--The cells of the body need water, alb.u.min, fat, sugar, and minerals for food. We sometimes eat sugar alone, and we drink pure water. But most of our food is a mixture of all five kinds of food. Food comes from animals and plants.

=29. Milk=.--Milk is the best food known. It contains just enough water, alb.u.min, fat, sugar, and minerals. Babies and young mammals live on milk alone. A man can live upon four quarts of milk a day. In sickness, milk is the very best food for men, as well as for babies.

The alb.u.min of milk becomes hard when the milk sours. This makes _cheese_. The fat of milk rises to the top. We call it _cream_. When cream is churned, the pure fat comes together in a lump. Pure fat of milk is called _b.u.t.ter_. Cheese and b.u.t.ter are both good foods.

=30. Eggs.=--Eggs are also good food. The white of an egg is almost pure alb.u.min. The yolk is alb.u.min and fat. Eggs have no starch or sugar.

They are not a perfect food, for some sugar must be eaten. But they can be quickly digested and they produce a great deal of strength.

=31. Meat.=--Meat contains alb.u.min and fat, but no sugar. Fish, oysters, and clams are like meat. They all make good food. Boys and girls should eat milk, eggs, and meat. These foods are the best to give strength to the body. Nearly all food from animals is more quickly digested and gives more strength than food from plants.

=32. Bread.=--White bread is a food made from wheat. The wheat is ground to flour. Flour is mixed with water, and yeast is added. The yeast makes a gas, and the gas puffs up the wet flour and makes it full of holes. The holes make the bread _light_. Then bread is baked.

Rye or corn meal makes good bread. Cake, biscuit, and pancakes are much like bread. Sometimes in place of yeast, baking powder is used to make the bread or cake light.

=33. Meal.=--Oatmeal, corn meal, and cracked wheat and rice are sometimes boiled, and eaten with milk. Bread, biscuit, oatmeal, and corn meal are made from grain. All are very much alike. The cooking makes them look and taste different, but yet they are nearly the same.

=34. Why we need grain food.=--All kinds of grain have much alb.u.min, but only a little fat. But all have a great deal of starch. By digestion the starch becomes sugar. Grain is a good food because it has starch or sugar. Animal foods have no sugar, so we eat grain food with them. The two together make the most nouris.h.i.+ng food. Potatoes have a great deal of starch and only a little alb.u.min. They also are good food with meat.

[Ill.u.s.tration: =A healthy man needs as much food as this every day.=]

A person cannot live well upon plant food alone, for it has too much starch and sugar, and too little alb.u.min and fat. We need nearly equal parts of alb.u.min, fat, and sugar. A mixture of bread, meat, eggs, vegetables, and milk makes the best food.

=35. Fruit.=--Fruit, like apples, peaches, and plums all have sugar.

They taste good, and give us an appet.i.te for other kinds of food.

They have little alb.u.min or fat.

=36. Salt.=--There is enough mineral matter in all food, and we do not have to eat iron or lime or soda. But we do need some more salt. Even animals need salt. Salt makes food taste good, and helps its digestion.

[Ill.u.s.tration: =People are made sick by drinking water from such a well.=]

=37. Water.=--Water is also a food, for it forms the most of our bodies. All food has water. Even dry crackers contain it.

=38. Pure water.=--Water in a well runs through the dirty earth, and yet is clear and pure. This is because sand holds back the dirt. But sometimes slops from the house, and water from the barn yard, soak through the soil until the sand is full. Then the well water will be dirty and poisonous. People are often made sick by drinking such water. In cities the dirt fills all the soil and spoils the water. So the water must be brought from the country in large pipes.