All foods are composed of certain chemical elements; namely, carbon, oxygen, hydrogen, nitrogen, sulphur, phosphorus, iron, magnesium, potassium, chlorine, sodium, calcium, with traces of various others. The manner in which these elements are combined and the amounts in which they occur determine the group to which the combination belongs, and give to the foodstuff its characteristic position in human nutrition. COMPOSITION OF THE FOODSTUFFS The chemical elements are combined in food and in the body, as: (a) carbohydrates, composed of carbon, oxygen and hydrogen; (b) fats, composed of carbon, oxygen and hydrogen; (c) proteins, composed of carbon, oxygen, hydrogen, nitrogen and sulphur; (d) water, composed of hydrogen and oxygen; (e) mineral salts. The first three foodstuffs constitute the Organic Food group. The last two include the remaining chemical elements, calcium, phosphorus, sodium, potassium, chlorine, magnesium, iron and traces of others which make up the Inorganic Food group. Each of the foodstuffs belonging to the organic group is capable of being burned in the body to produce heat for: (a) the maintenance of the body temperature; (b) internal and external work. Neither water nor mineral salts alone can be burned to produce heat; nevertheless, they enter into the composition and take part in every function performed by the carbohydrates, fats and proteins; therefore one foodstuff cannot be said to be of greater importance than another, since the needs of nature are best met by a judicious combination of all. However, the wear and tear of life can be more efficiently accounted for, and the strain upon the organism reduced more nearly to a minimum when the various foodstuffs are furnished in amounts which science is proving to be necessary for the health and well-being of the organism. The sixth essential food substance, the ~Vitamines~, together with the adjustment of the five foodstuffs just mentioned--the amounts and types of each in the dietary which will assure the body of the best results--has been, and still is a subject of grave interest. Even on the most perfect adjustment of these foodstuffs, the diet would fail to give the desired results without the inclusion of the sixth, or vitamine factor, which has proved to be essential for the growth and development of the normal body, as well as for its protection against certain deficiency diseases.