25. The value of cereals. Why is it that the cereal grains have been valued so highly from the earliest times? What makes them so much better than other vegetable foods, and why are some of them superior to others? The fact that these plants ripen their seeds within a few months after planting, and under favorable conditions yield such a large return for the labor bestowed upon them, will doubtless partly account for the high favor in which they are held; but as much the same may be said of other vegetables of far less value as food, there must be some more important reasons. In order to understand these, we must know something of the chemical composition of cereals; that is to say, we must learn what substances are to be found in the different grains and in what amount.