13 



PreliniiiKirv to the expeiiiiK'ntal work .stutistics were compiled 

 reo-iirdiiiu- the food supply of the whole institution. These are given 

 in Till tie 36 of the Appendix and sunnnurized on page 72. These 

 statistics are for the fiscal 3'ear just preceding the time of the dietary 

 studies, and consequently do not strictly apply to the time during 

 which the studies were made. Unfortunately, when the studies were 

 completed there w^as no opportunity to compile similar data for the 

 year in which the studies were conducted, but from a cursory exami- 

 nation of the accounts it seemed fair to consider that the supplies for 

 the two years did not dili'er materially in actual nutritive value. 



EXPERIMENTAL METHODS. 



Previous publications of this Office" have given detailed discussions 

 of the composition and nutritive values of food, the functions of tlic 

 different nutrients, the objects and methods of making dietary studies, 

 etc. The following sunnnarized statements will therefore suffice here: 



Food is useful to the body only so far as it supplies to it the mate- 

 rials which it uses for growth and for repairing its Avastes, replacing 

 worn-out tissues, and supplying energy for nmscular woi'k. The 

 materials so used are protein or nitrogenous material, fats, carbohy- 

 drates, and various salts. In addition the body requires the oxygen 

 of the air, and water, Avhich, though necessary for physiological 

 reasons, is not usually called a nutrient. Some or all of these nutri- 

 ents arc present in all foods, though occurring in varying forms and 

 proportions in difl'ercnt materials. Just how^ the different nutrients 

 are used in the body in all cases may be somewhat uncertain, hut it 

 seems undoubtedly true that under ordinaiy conditions protein is used 

 for building up and repairing muscular tissue, while the fats and 

 carbohydrates, together with the surplus of protein, are oxidized to 

 yield the energy for motion and muscular work; though if the quanti- 

 ties of nutrients are larger than are immediately needed the surplus 

 may be stored in some form (chiefly fat) for future use. Salts are use- 

 ful for forming bone and other parts of the body and are doubtless 

 used in other ways also. 



The final object of a dietary study is in brief to determine the quan- 

 tities of nutrients and energy in the diet of a given nund)er of persons 

 for a definite period. The usual method of conducting a dietary study, 

 in a family for instance, includes (1) determinations of the amounts of 

 all the different food materials in store at the beginning of, purchased 

 during, and remaining on hand at the end of the period of study; (2) 

 determinations of the kinds and amounts of kitchen and table wastes, 

 with analyses where practicable; and (3) a record of the weight, age, 

 sex, and occupation of the different members of the group, and the 



ff See list on cover. 



