In the descriptions just given of the various foodstuffs, especially in regard to their function in the body, it is readily seen that no one foodstuff is used to the exclusion of another. It is further seen that in the upkeep of the body, which includes not only the building and repairing of its tissues, but the running of the engine and maintaining of its normal temperature, the organism uses each and all of the organic food substances for the production of heat. Furthermore, while the tissues are chiefly built from protein material, and physiology teaches that protein can be built only from other protein, these tissues contain a certain amount of carbohydrate, fat, mineral salts, and water; this furnishes distinct evidence that the building of the cells and tissues of the body cannot be accomplished by means of protein alone, but by the judicious balancing of all the foodstuffs in the dietary. Science has gone even further than this, as has just been demonstrated, and has proven that without the substances known as vitamines the normal growth and development in the young would be arrested, and that the maintenance of the adult body would be impaired. It has also proven that certain diseases owe their development to deficiencies in the vitamine supply to the body. PROBLEMS (a) Outline briefly what is believed to be the essentials of an adequate dietary. (b) List the fuel foods and show their most economical source. (c) List the best sources of the complete proteins. (d) Show how the incomplete protein foods may be made adequate for growth. FOOTNOTES: [1] One quart of milk contains more calcium than a quart of clear saturated solution of lime water. [2] For complete list, see Eddy's Table, in Appendix. [3] "Chemistry of Food and Nutrition" (revised edition), by Sherman. [4] Scientists are proving the need for certain vitamine factors in the diet in order that the growth and development of young tissues and the repair of adult tissues may proceed. The part played by these substances will be discussed later. [5] "Chemistry of Food and Nutrition" (2d ed.), by Sherman. [6] "The Basis of Nutrition," by Graham Lusk. [7] "Food Products," by Henry Sherman. [8] Abstracts made from thirteen papers from the Laboratory of Physiological Chemistry, Jefferson Medical College, Philadelphia; published in the "American Journal of Physiology and Science," by Minna C. Denton. U.S. Department of Agriculture. [9] "Chemistry of Food and Nutrition" (revised), p. 333, by Henry Sherman. [10] "Chemistry of Food and Nutrition" (revised edition), by Sherman. [11] "The Vitamine Manual," p. 64, by Walter Eddy [12] Courtesy of Dr. E. V. McCollum. [13] Milk from cows whose diet has been deficient in vitamines shows a like deficiency in vitamine content--the same is true of mother's milk. [14] "The Vitamine Manual," p. 64, by Walter H. Eddy. CHAPTER II THE FUEL VALUE OF FOOD