Handbook of domestic science and household arts for use in elementary schools

To show this let perfectly clear bones simmer for several hours. Let each child examine the water. Remove the bones. Evaporate the greater portion of the water by boiling. Set the rest away to cool. Show the class the jelly-like resulting gelatinoid. It will dissolve again by warming it. To demonstrate the extractives, let each child examine a small piece of raw lean meat, noting in passing the muscle fibres and connective tissues. Let each put her piece in cold, slightly salted water, watching the extraction of the juices, and later examining both the meat and the liquid. The object of these experiments has been merely to familiarize the children with the various forms of protein, to add to his vocabulary the words j)ro;e/fZs and extractives, with possibly the terms albuminoids and gelati)ioids, although these last terms are not nearly so essential as the facts concerning them. The Carbohydrates By this term is meant compounds made up of the carbon, and hjalrogen and oxygen, in certain definite proportions. In this class may be included starch, the sugars, cellulose. For facts concerning them and methods of teaching see the chapter on Starchy Foods. The Hydrocarbons Facts. — The hydrocarbons (fats and oils) contain the same chemical elements as the carbohydrates, viz., carbon, hydrogen, oxygen, but the relative proportion of the oxygen is much smaller. For their combustion in the body, therefore, more oxygen must be taken from the air. Consequently from them a greater quantity of heat is evolved. They are obviously the most efficient fuel foods, and are, therefore, relatively more used in the northern climes, and in dead of winter, than in warmer regions and in summer. Luckily instinct taught us this long before science demonstrated it. Fats are also stored up in the body for times of need. It is thought that they pass through the mouth and stomach absolutely unchanged. Even the bile and pancreatic juice seem only to emulsify it, and this, after all, is merely a physical change. The finely divided oil is carried by the blood and deposited in the spaces between the muscle bundles, ready to be used when needed. Fat is found in most food materials. It is found in large quantities in meats (tallow, lard) ; in milk (butter) ; in various vegetables, such as cotton seed, olives, etc. Method. — Show the children fat in connection with meal. What is it ? What color is it ? Have you ever seen it yellow in color ? What did that indicate ? (Age.) Heat the fat. What change takes place ? Do we get fats or oils in vegetable food ? Why do you think so ? Distribute an oily seed, such as nutmegs, cotton seed, peanuts, or nuts of any kind, squash. If necessary tell the children to remove the outer coat. Prick with a pin. Oil will at once ooze out. Tell me at what time of the year you are most inclined to eat fats. What people eat fat more eagerly than we do ? "Why? What then is the use of fat food to us? Are the other foods, too, available as fuels ? (Even the proteids may be consumed for fuel.) What advantage, then, to eat fats when food fuel is needed ? (To save the proteids for their more important and untransferable work — of building up the tissues.) Inorganic Food Materials