Sugars are of common occurrence in the vegetable world in the fruits and juices of many plants. Pure grape juice may contain as high as 25 per cent of glucose though usually it is not so concentrated. Glucose is also found in considerable amount in sweet corn and onions. It is not so sweet as cane sugar (sucrose). Fructose is one of the sweetest of sugars, and helps to give honey its great sweetness. _Lactose_ or milk sugar is found chiefly in milk. It is the least sweet of all the sugars. If there were as much cane sugar in milk, we should soon grow tired of it because it would be too sweet. It is sometimes added to milk to make its fuel value higher, especially in case the milk has been diluted, as in the diet of babies and invalids. _Maltose_ or malt sugar is formed from starch in germinating seeds. _Sucrose_ or cane sugar is most commonly manufactured from sugar cane and sugar beets. To a much smaller extent it is made commercially from the sugar maple, sorghum cane, and sugar palm, and it is found in considerable amount in some common fruits and vegetables. Its manufacture forms a great industry, and its consumption is enormous, some ten million tons coming into commerce annually, and this does not represent the total consumption. Figure 48 shows the composition of several common sugars. Notice that the granulated sugar is a pure foodstuff, being 100 per cent carbohydrate, while all the others contain traces of protein, ash, and water. Sugar is a fuel food, exclusively, like olive oil and other pure fats. [Illustration: FIG. 48.——Composition of sugars.] Sugar is a valuable food material, but should not be used in excess; the tendency in the United States is rather toward an excessive use of sugar. It is liable to cause an acid fermentation in digestion, when taken in large amounts, and is sure to irritate the stomach. It should be well diluted by other foods. The amount that may be eaten daily varies for most people from two ounces for young children to four ounces for adults, but many people cannot eat these amounts without more or less irritation of the stomach. It is a common practice to oversweeten cakes and desserts, the sweetness of the sugar often disguising other agreeable flavors. The liking for sweets should be well under control, for the eating of too much sugar is a habit easy to form, and one which crowds out other valuable foods. _Cane Sugar_ is sold both brown and white, and is manufactured in powdered, granulated, and solid form, the latter usually cut in cubes or dominoes.