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Table of Contents

The following are familiar examples of compounds of each of the four principal classes of nutrients:

Protein:

Proteids.

Albuminoids, e.g., albumen of eggs; myosin, the basis of muscle (lean meat); the albuminoids which make up the gluten of wheat, etc.

Gelatinoids, constituents of connective tissue which yield gelatin and allied substances, e.g., collagen of tendon; ossein of bone.

"Nitrogenous extractives" of flesh, i.e., of meats and fish. These include kreatin and allied compounds, and are the chief ingredients of beef tea and most meat extracts. Amids: this term is frequently applied to the nitrogenous non-albuminoid compounds of vegetable foods and feeding stuffs, among which are amido acids, such as aspartic acid and asparagin. Some of them are more or less allied in chemical constitution to the nitrogenous extractives of flesh.

Fats.

Fat of meat: fat of milk; oil of corn, wheat, etc. The ingredients of the "ether extract" of animal and vegetable foods and feeding stuffs, which it is customary to group together roughly as fats, include, with the true fats, various other substances, as lecithians, and chlorophylls.

Carbohydrates, sugars, starches, celluloses, gums, woody fibre, etc.

Mineral matter.

Potassium, sodium, calcium and magnesium chlorids, sulphates and phosphates. (Atwater).

The terms (a) "nitrogenous" and (b) "carbonaceous" are frequently used to designate the two distinct classes of food, viz.: (a) the tissue builders and flesh formers; (b) fuel and force producers.

Each of these classes contains food material derived from both the animal and vegetable kingdom, although the majority of the animal substances belong to the nitrogenous, and the majority of the vegetable substances to the carbonaceous group.

Therefore, for practical purposes, we will confine ourselves to the more general terms used in Atwater's table.