Thus we see that each constituent of the food substance fulfills a specific purpose, and the secret of a correct and nutritious diet lies in the selection of such foods as will furnish the proper proportion of each constituent to serve the purpose for which it is designed. Any deviation from this rule must of necessity result in digestive disturbance, more or less, and although one or two digressions from the path of correct alimentation may not result in anything worse than a slight inconvenience, yet persistence in dietetic errors will inevitably terminate in physical demoralization. Authorities differ as to the actual proportion the nutritive ingredients should bear to each other in the daily ration; but after comparing the statements advanced by different food experts. We think the following figures will represent a fair average of the various tables. The reader will see that 100 parts of carbo-hydrates is taken as the basis of calculation, the figures opposite the other ingredients representing the proportion they should bear to the basic figure. Carbo-hydrates (carbonaceous material, starch, sugar, etc.), fat, and heat formers, 100 parts. Proteids (nitrogenous material) muscle, tissue and brain formers 40 parts. Fats (animal fats, butter, etc.), fuel formers 32 parts. Mineral salts, 6 parts. Water 670 parts. With the above table in mind, it will be easy to select foods that will furnish, when combined, the proper proportion of each ingredient--that is--approximately, and to assist in the selection, we subjoin a condensed list of the more important articles of food, showing the percentage of each ingredient, as proved by analysis. We would call attention to the fact that animal foods may slightly differ in the ratio of the ingredients, owing to the food upon which the animal has been raised, and its physical condition; and, owing to peculiarities of soil, vegetable foods may differ in like manner, but for practical purposes it will be found sufficiently correct. IN 100 PARTS. *Lean Beef Proteids. 20.2 Starches. 0.0 Fats. 3.6 Salts. 2.0 *Fat Proteids. 16.9 Starches. 0.0 Fats. 3.6 Salts. 2.0 *Mutton Proteids. 17.1 Starches. 0.0 Fats. 5.7 Salts. 1.3 *Veal Proteids. 18.8 Starches. 0.0 Fats. 4.4 Salts. 0.5 *Pork Proteids. 14.5 Starches. 0.0 Fats. 37.3 Salts. 0.8 *Poultry Proteids. 21.0 Starches. 0.0 Fats. 3.8 Salts. 1.2 *Smoked Ham Proteids. 24.0 Starches. 0.0 Fats. 36.5 Salts. 10.1 *Mackerel Proteids. 23.5 Starches. 0.0 Fats. 6.7 Salts. 1.0 *Cod Proteids. 27.0 Starches.0.0 Fats.0.3 Salts.22.0 *White of Egg Proteids. 20.4 Starches. 0.0 Fats. 0.0 Salts. 1.6 *Yolk of Egg Proteids. 16.0 Starches. 0.0 Fats. 30.7 Salts. 1.3 *Cow's Milk Proteids. 4.2 Starches. 4.5 Fats. 3.7 Salts. 0.7 *Cheese Proteids. 28.0 Starches. 1.0 Fats. 23.0 Salts. 7.0 *Butter Proteids. 2.0 Starches. 1.0 Fats. 85.0 Salts. 1.0 *Cabbage Proteids. 5.0 Starches. 7.8 Fats. 0.5 Salts. 1.2 *Asparagus Proteids. 1.9 Starches. 2.7 Fats. 0.2 Salts. 0.5