CHAPTER VII
FORM IV: JUNIOR GRADE (Continued)
STUDY OF FOOD
The pupils have been working with some of the well-known foods in all of their recipes and should have a fair knowledge of how to prepare them in simple ways for the table. It is now time for them to learn what these foods contain for the use of their bodies. Much of this part of the work can be taught in rooms without special equipment. An earnest teacher, with a few articles from home, can make the study interesting and valuable.
A series of lessons will be necessary for this purpose. The amount of work to be taken at one time is suggested, but this should be judged by the teacher. As in other lessons on theory, the remaining time of the lesson period should be used in practical work. Suggestions for such practical work are given under the lesson on "The Kitchen Fire", page 92.
Practice lessons, to give variety and sustain interest, should be interspersed between these lessons as desired.
LESSON I
USES OF FOOD
The lesson may be introduced by asking the class to think in what way the body of a healthy baby, who is fed regularly, will have changed at the end of six months. It will be larger; it will have more flesh, more bone, more hair, etc. We want to get a name that will apply to any part of the body. No matter which part we examine through a microscope we find the same fine and beautiful texture, and to this we give a name similar to that given to fine, thin paper. We call it _tissue_--hair tissue, bone tissue, flesh tissue.
What has food done to the baby's tissues? It has enlarged its tissues; the child has grown larger. To the enlargement, or growth, of the tissues, we may apply the term, _build_, suggested by the building of a house. Then what may we say food does for the tissues of the body? We may say that _food builds the tissues of the body_.
Think of some persons who have taken food every day, and yet as long as you have known them they have not increased in size. What has food done for their tissues? The class must be told that the tissues of our bodies wear out through use, and that food has furnished the material to replace the worn-out parts. What do we say we are doing to clothes when we replace the worn parts? We are mending or repairing them. What does food do for our worn-out tissues? _Food repairs the tissues of the body._
Do not think any more about the tissues of the body. Suppose you had not been able to get any food for several days. In what way would you be different from what you are now? You would not be as strong. Food gives strength or energy by being burned inside the body. There is a fire burning in our bodies all the time we are alive, the fuel being food.
What do we require from the fire in our homes? We require heat. The fires in our bodies give us heat also. Any fire gives off both heat and energy. State another use of food to the body. _Food produces heat and energy in the body._
But food does more for the body; it contains substances to keep our bodies in order. Suppose the clock gets out of order and does not keep good time, what does the watchmaker do to it? He regulates it. That is what certain kinds of food do for us. What then is another use of food?
_Food regulates the body._
Name the uses of food to the body.
1. It builds the tissues.
2. It repairs the tissues.
3. It produces heat and energy.
4. It regulates the body.
How then can we judge if a substance be a food? By deciding that it performs one of these duties in the body.
LESSON II
NECESSARY SUBSTANCES IN FOOD
The names of the substances in food which supply the material for the different uses of the body should be taken next.
1. _For building and repairing._--(1) Mineral matter--used largely in hard tissues. (2) Nitrogenous matter, or protein--used largely for flesh. (3) Water--used in all tissues.
2. _For fuel._--Carbonaceous matter (starch, sugar, fat).
3. _For regulating._--Mineral matter, water.
NOTE.--The teacher should call attention to the fact that few foods contain all these substances, some have nearly all, some have only one, some two or more. In order to get all, we must eat a variety of foods. The class is now ready to consider the well-known foods, in order to find out which of these necessary substances each food contains, and to obtain a general idea of their comparative food values.
SOURCES OF FOOD
All nature supplies us with food. The three great divisions of nature are animal, vegetable, and mineral, and from each we obtain food, though most largely from the animal and vegetable kingdoms.
Animal food is some part of an animal's body or some product of an animal: examples--meat or fish, milk, eggs.
Vegetable food is some part of a plant: examples--vegetables, fruit, seeds.
Mineral food is some constituent of the earth's crust used as food. This mineral food is obtained by drinking water which in coursing through the earth has absorbed certain minerals, by eating plants which have absorbed the minerals from the soil, or by eating animal food which was built from plant food.
This preliminary survey of the sources of all our food gives the pupils a basis for classifying the foods with which they are familiar. They may be given exercises in doing this, and will not only find them interesting, but most useful as nature study.
STUDY OF THE COMMON FOODS
In beginning the analysis of the common foods, it must be remembered that the pupils have no knowledge of chemistry, and that what is found in each food must be discovered through the senses (seeing, smelling, tasting, feeling), or through a process of reasoning.
The pupils should also feel quite sure of what they are setting out to do; they are going to examine some particular, well-known food, to find which of the necessary food substances it contains. The food substances for which they are looking are water, mineral matter, nitrogenous matter, and carbonaceous matter (sugar, starch, fat).
It is better to provide each pupil with a sample of the food to be studied, but where conditions make this difficult, the one used by the teacher will suffice.
STUDY OF MILK
LESSON I
COMPOSITION
Milk is the best food to examine first, because it contains all the food elements except starch and because these can be easily found.
The pupils may each be asked to bring a half cup of milk from home. It may be allowed to stand in glasses while other work is taken.
When ready for the lesson, ask the pupils to look at the contents of the glass, and they will observe a difference of colour where the cream has risen. Nature itself has divided the milk into two parts. Pour off the top part and feel it. It feels greasy. Butter is made from this part. We have found _fat_--a carbonaceous food.
Move the milk around in the glass and let the pupils see that it is a liquid. Tell them that all liquid in a natural food is mostly water. We have, therefore, another food substance--_water_, a builder and regulator.
Let the pupils compare a glass of water with a glass of skimmed milk, and they see that something is dissolved in the water of the milk, giving it the white colour. Show them a glass of sour milk, where the white substance is separate from the water. Get the names curd and whey.