“Oh, but, Bertram, it's serious, really,” urged Billy, looking genuinely distressed. “Why, it says that what you eat goes to make up what you are. It makes your vital energies. Your brain power and your body power come from what you eat. Don't you see? If you're going to paint a picture you need something different from what you would if you were going to--to saw wood; and what this book tells is--is what I ought to give you to make you do each one, I should think, from what I've read so far. Now don't you see how important it is? What if I should give you the saw-wood kind of a breakfast when you were just going up-stairs to paint all day? And what if I should give Uncle William a--a soldier's breakfast when all he is going to do is to go down on State Street and sit still all day?” “But--but, my dear,” began Uncle William, looking slightly worried, “there's my eggs that I _always_ have, you know.” “For heaven's sake, Billy, what _have_ you got hold of now?” demanded Bertram, with just a touch of irritation. Billy laughed merrily. “Well, I suppose I didn't sound very logical,” she admitted. “But the book--you just wait. It's in the kitchen. I'm going to get it.” And with laughing eagerness she ran from the room. In a moment she had returned, book in hand. “Now listen. _This_ is the real thing--not my garbled inaccuracies. 'The food which we eat serves three purposes: it builds the body substance, bone, muscle, etc., it produces heat in the body, and it generates vital energy. Nitrogen in different chemical combinations contributes largely to the manufacture of body substances; the fats produce heat; and the starches and sugars go to make the vital energy. The nitrogenous food elements we call proteins; the fats and oils, fats; and the starches and sugars (because of the predominance of carbon), we call carbohydrates. Now in selecting the diet for the day you should take care to choose those foods which give the proteins, fats, and carbohydrates in just the right proportion.'” “Oh, Billy!” groaned Bertram. “But it's so, Bertram,” maintained Billy, anxiously. “And it's every bit here. I don't have to guess at it at all. They even give the quantities of calories of energy required for different sized men. I'm going to measure you both to-morrow; and you must be weighed, too,” she continued, ignoring the sniffs of remonstrance from her two listeners. “Then I'll know just how many calories to give each of you. They say a man of average size and weight, and sedentary occupation, should have at least 2,000 calories--and some authorities say 3,000--in this proportion: proteins, 300 calories, fats, 350 calories, carbohydrates, 1,350 calories. But you both are taller than five feet five inches, and I should think you weighed more than 145 pounds; so I can't tell just yet how many calories you will need.” “How many we will need, indeed!” ejaculated Bertram.