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plasm of the active tissues, (3) as salts, held in solution in the fluids of the body, giving these fluids their characteristic influence upon the elasticity and irritability of muscle and nerve, supplying the material for the acidity or alkalinity of the digestive juices and other secretions, and yet maintaining the neutrality or slight alkalescence of the internal fluids as well as their osmotic pressure and solvent power." In the study of nutrition very careful attention has been given to the rôle which the various salts, as the chlorides, sulfur and phosphorus compounds, calcium and iron compounds play in the process of animal nutrition. These inorganic materials are abundant in both vegetable and animal food-stuffs, and their occurrence, and relative quantity as a part of the diet should be always considered.

HEAT UNITS OF FOOD COMPOUNDS

Since reference is frequently made to the amount of energy available from different foods it is important briefly to define the use of this term as used in dietetics. The unit of energy adopted for a comparative study of foods is the "calorie." This is the energy in terms of heat which is sufficient to raise the temperature of 1 pound of water 4° F, or to raise the temperature of one kilogram of water from o° to 1° C. This energy or the number of heat units is determined by the use of an instrument called a calorimeter, in which a known weight of the food is actually burned, and the heat evolved is used to raise the temperature of a known weight of water. By very elaborate experiments it has been shown that there is a close relation between the results obtained by the calorimeter, and the actual energy produced in the body by the proper digestion and assimilation of the food.

As an illustration of the use of this energy unit, the energy value of a pound of edible material from a few food-stuffs is quoted from Jordan.2

1 Chemistry of Food and Nutrition, Sherman.

* Principles of Human Nutrition, Jordan, p. 163.

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The inspection of these values affords an opportunity for the comparison of different foods. The author in discussing energy points out that it is important also to distinguish between the heat produced when substances are burned in the calorimeter, and the heat or energy that is available when used in the body, as it never happens that the combustible portion of a ration is entirely consumed in the body. This is the case because the food is never all digested, the digested proteins are never fully burned, and there is usually an escape of unconsumed gases from the alimentary canal, especially in the case of farm animals. As actual work is performed in the process of digestion, the term "net energy" has been introduced to apply to that amount of energy which is available, after that used up in the digestion and preparation of the food for use in the body has been subtracted.

Planning of the Diet; Vitamines

Although it is not the province of this work to discuss at length dietetic topics, something should be said in regard to the newer knowledge in regard to nutrition. From the researches of Fischer, about the year 1900, it was shown that there is a great difference in the composition of proteins from different sources.

We now regard most proteins as bodies capable of being resolved into at least 18 simple digestive products, called amino-acids, which may be absorbed into the blood. Most natural foods contain several of these proteins, but there are some foods which appear to be lacking in one or more of these indispensable constituents of an adequate diet. "The proteins of any single foodstuff may be regarded as biologically complete, but their biological values differ greatly, depending on the yield of the several aminoacids which can be obtained from them." It has also been shown that the so called “deficiency diseases", such as scurvy, pellagra rickets and beri beri, are due to a faulty diet. Experiments on the lower animals2 have also show that growth could be maintained when butter fat or egg fat was contained in the food, but not satisfactorily with such fats as that from lard or with. vegetable fats. Further experiments by McCollum, Davis and others, indicate that, in addition to the proteins, fats, carbohydrates and mineral salts, the diet must also contain two as yet unidentified substances, or groups of substances.

Sources of Food

The "vitamine" hypothesis of Funk, has led to a further study of malnutrition as referred to a faulty diet, and although these investigations have really only just begun, it seems to be demonstrated that deficiency diseases are due to the shortage of one or the other of the substances, that have been provisionally named as "fat-soluble A. and Water-soluble B. "It should be noted that seed mixtures, no matter what seeds are used, will never induce complete nutrition. Seeds, even with roots, tubers and meat, are not adequate for the nutrition of an animal during growth. The satisfactory nutrition of the animal demands not only a combinations of seeds, tubers and roots, but a sufficient amount of the leaves of plants, and an abundance of milk.

1 The Newer Knowledge of Nutrition, p. 5.

2 Journ. Biolog. Chem. xv, p. 167.

3 McCollum. Loc. Cit.

Investigations recently made show that the average diet of the people of the United States is derived from the following sources;

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CHAPTER II

THE COMPOSITION OF CEREALS AND THE MANUFACTURE OF STARCH

The term cereals includes the plants of the grass family (Graminea) which are used as food. Wheat, rye, oats, barley, rice, corn (maize) and millet belong in this class, and buckwheat and quinoa, although not grasses, are here considered. The grain consists of the germ, and the endosperm with its coverings, which are the parts most utilized for human food.

WHEAT (Triticum vulgare)

Considered from the viewpoint of general use, there is no cereal of so great importance as wheat, for not only does it grow readily in the temperate climate where the active peoples of the world are found, but its products are peculiarly adapted for the food of man.

The origin of wheat is lost in antiquity. Wheat was cultivated by the ancient Egyptians and Chinese, was grown in Mesopotamia and has been found in the pre-historic lake-dwellings of Switzerland and Italy. The present form of wheat may be as naturally found, or it may be derived from a wild plant some varieties of which, improved by cultivation, are still found. It was introduced into Great Britain by the Romans.

Varieties

The botanist recognizes three species which he calls the grain wheat, Polish wheat, and common wheat, and of each of these, there are numerous varieties. Although the quality is much

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