With this basis, to give us some understanding of the complicated and delicate machinery with which we must work, the question arises, what food contains all these constituents, and what its amount and character must be. The answer to this question will help us to form an intelligent plan for providing a family with the right nutrition.
FOOD AND ITS LAWS.
We have found, that, in analyzing the constituents of the body, water is the largest part; and turning to food, whether animal or vegetable, the same fact holds good. It forms the larger part of all the drinks, of fruits, of succulent vegetables, eggs, fish, cheese, the cereals, and even of fats.
Fat is found in butter, lard, drippings, milk, eggs, cheese, fish, meat, the cereals, leguminous vegetables,—such as pease and beans,—nuts, cocoa, and chocolate.
Sugar abounds in fruits and vegetables, and is found in milk and cereals.
Starch, which under the action of the saliva changes into glucose or grape-sugar, is present in vegetables and cereals.
Flesh foods, called as often nitrogenous foods, from containing so large a proportion of nitrogen, are made up of fibrine, albumen, caseine, gelatine, and gluten; the first four elements being present in flesh, the latter in vegetables.
Salts of various forms exist in both animal and vegetable food. In meat, fish, and potatoes are found phosphorus, lime, and magnesia. Common salt is largely made up of soda, but is found with potash in many vegetables. This last element is also in meat, fish, milk, vegetables, and fruits. Iron abounds in flesh and vegetables; and sulphur enters into albumen, caseine, and fibrine.
The simplest division of food is into flesh-formers and heat-producers; the former being as often called nitrogenous food, or albumenoids; the latter, heat-giving or carbonaceous foods. Much minuter divisions could be made, but these two cover the ground sufficiently well. For a healthy body both are necessary, but climate and constitution will always make a difference in the amounts required. Thus, in a keen and long-continued winter, the most condensed forms of carbonaceous foods will be needed; while in summer a small portion of nitrogenous food to nourish muscle, and a large amount of cooling fruits and vegetables, are indicated; both of these, though more or less carbonaceous in character, containing so much water as to neutralize any heat-producing effects.