Our objection to nut-meats applies to all forms of concentrated foods, that is, that they do not give the digestive functions the proper amount of exercise. They do not afford sufficient opportunity for mastication, hence the food is not properly insalivated. And, again, in normal conditions, Nature demands a certain amount of bulk, that the digestive organs may have something to contract upon. It is the nature of the muscular structures to grow if exercised, and there is no reason to doubt that the stomach and intestinal muscles respond to this stimulus. Bulk is especially necessary in the intestinal canal, to supply a certain amount of irritative stimulation, for the purpose of exciting peristalsis. That is one reason why whole wheat bread is preferable to white, on account of the bran, which not only supplies the bulk, but favors elimination by its irritative action.
Before proceeding any further we would call attention to the following table, showing the nutritive ingredients in food substances, and their several functions. The ingredients are classified in four divisions: 1, Proteids; 2, Fats; 3, Starches, or carbo-hydrates; 4, Mineral matters. This is the main classification; but to enable it to be better understood, we subdivide it as follows:
{ a. Albuminoids: e. g. albumen (white of { egg); casein (curd) of milk; myosin, { the basis of muscle (lean meat); gluten { of wheat, etc. { b. Gelatinoids: e. g. collagen of tendons; ossein { of bones, which yield gelatin or glue. Protein. { (Meats and fish contain very small quantities { of so-called “extractives.” They { include kreatin and allied compounds, { and are the chief ingredients of beef-tea { and meat extract. They contain nitrogen, { and hence are commonly classed { with protein.)
Fats. { e.g. fat of meat; fat (butter) of milk; olive { oil; oil of corn, wheat, etc.
Carbohydrates. e.g. sugar, starch, cellulose (woody fibre).
Mineral Matters. { e.g. calcium phosphate or phosphate of lime; { sodium chloride (common salt).
In this classification, water is not taken into account, for the reason that it is not a true nutrient, although of vital importance to the body. Now, let us consider what ultimately becomes of these substances--how Nature utilizes them in the physical economy. Protein is used to build up the solid tissues of the body, the muscles and tendons. It is also a source of nutrition for brain and nerve substance, and partially serves as fuel. Fats simply form fatty tissue and serve as fuel to maintain the heat of the body, by combustion or oxidation. Carbo-hydrates mainly serve as fuel, owing to the large percentage of carbon they contain, which readily unites with the oxygen. The mineral matters, which are also largely obtained from water, are employed in the formation of bone, and are also utilized in the blood and in other ways.