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 Studies based on Table.—What nuts are rich in proteids? What fruits? What animal foods? What legumes? What grains? What foods are rich in fats? What are rich in carbohydrates? Which grains have much starch? Which nut? Which fruits have much sugar? A family was living chiefly on corn bread, potatoes, syrup, cakes, and sweetmeats: what two of the four food stuffs were deficient in their diet? Another family lived chiefly on fat pork, bread, rice, vegetables, and fruit: which food stuff was deficient? A dozen eggs weigh 1-1/2 lb. Which give cheaper nourishment, eggs at 15 cents a dozen or beef at 15 cents a pound? Which is cheapest among the foods abounding in proteid? Fat? Carbohydrates? Which is cheaper food, a pound of beef at 20 cents or a pound of pecans at the same price? (Fig. 101.) What food contains most water? Least water? Which of the foods abounding in proteid is costliest? Cheapest? Notice that nearly all foods containing much proteid are costly. Water and woody fiber are not counted as nutriment. What weight of nutriment in 1 oz. of cow's milk? If a quart of whole milk costs 12 cts., what is a quart of skimmed milk worth?

How the Right Proportions of Fuel Foods and Proteid are reached by Different Nations.—Milk has an excess of nitrogen, and oatmeal an excess of carbon; oatmeal and milk form a popular food with the Scotch. Potatoes are mostly starch and water, and an Irishman who tried to live on potatoes alone would have to eat seven pounds a day to get enough proteid. The Irish peasant keeps a cow and chickens; by eating milk and eggs he gets along on half the amount of potatoes named above. The Mexicans eat bread made of corn meal, and supply the proteid by using beans as a constant article of diet. Hundreds of millions of people in Asia (the Hindus, Chinese, and others) subsist mainly on rice, which contains only five per cent of proteid and no fat; the chief addition they make is butter, or other fat, and beans, which contain vegetable proteid.

Outline of Digestion.—The food is made soluble in the alimentary canal and is absorbed by the blood vessels and lymphatics in its walls. This canal is about thirty feet long (Figs. 89, 90) and consists of—

(1) The mouth, where the food remains about a minute, while it is chewed and mixed with the saliva; the saliva changes a portion of the starch to malt sugar.

(2) The gullet, a tube nine inches long, running from