— 5 — 



the tables have been arranged so that they may be most easily used by 

 any who are unaccustomed to such work. 



Before proceeding with the study of dietaries it may not be out of 

 place to give a brief resume of the first principles, the A B C's, as it 

 were, of the subject, i. e., the objects of feeding — the chemical com- 

 position of the various parts of the body; and also the classes of food- 

 stuffs, with the offices the different ones perform in the body. 



OBJECTS OF FOOD. 



We all know that the young body, animal or human, requires food to 

 supply the material necessary for its growth. But beyond this, and 

 continuing during and past the growing stage, there is a current 

 wearing-out and breaking-down of all the various tissues of the body. 

 This loss must be supplied in order to keep the animal in a normal, 

 healthy condition. Not only must the worn-out tissue be replaced, but 

 the material, used as fuel in producing the energy necessary for carrying 

 on all voluntary and involuntary functions, must also be supplied. A 

 man who is doing hard physical work is using up a great deal of fatty 

 tissue, as well as muscle; but a man who is doing nothing (making no 

 voluntary exertion), also experiences a loss of tissue through the con- 

 stant production of the heat necessary for the maintenance of the 

 normal body temperature, and also for the Performance of all the 

 involuntary functions of the. body. Hence we might summarize the 

 objects of feeding as follows: 



1. To build up and maintain the body in its normal condition. 



2. To serve as a fuel-supply to be consumed in the body, producing 

 heat to keep it warm, or the energy (muscular or otherwise) necessary 

 for the Performance of work. 



3. To be stored for future use. 



COMPOSITION OF FOODS. 



In Order to see how these objects may best be carried out, we must 

 understand the composition of these tissues that need rebuilding, and 

 also the composition of the various foodstuffs at our command. Viewing 

 them side by side for the purpose of better comparison, we see, from a 

 general analysis, that each is composed of the same four main ingredi- 

 ents — water, mineral matters, nitrogenous and non-nitrogenous material. 



Water. — Water constitutes about two thirds of the weight of the body, 

 and enters into the composition of all its tissues and fluids. As it does 

 not form nearly that large a proportion of our ordinary cooked foods, 

 we can readily understand the necessity of its use as a separate part of 

 our diet. 



Mineral Matters. — The mineral matter comprises about 5 per cent of 

 the body, and has important functions to perform, such as entering into 

 the formation of the bones and teeth, regulating the density and taking 

 part in the functions of the blood and such other fluids of the body, as 

 the bile, Juices of the stomach, etc. In estimating food-values, the 

 mineral or inorganic ingredients are generally omitted, not on account 

 of any lack of importance of that portion of our food, but for the reason 



