'I'liK llri.LiniN. 13 



tliey are the basis of blood, and the sovirce of casein in milk; and 

 in the absence of sufficient quantities of fats and carbohydrates in 

 the food for the production of heat and energy, they are transformed 

 into fats, and perform the office of fats in nutrition. This latter 

 transformation may also result from an excess of protein. The 

 heat-producing poMX'r of protein is but little different from that of 

 carbohydrates ; the amount of fat it produces is probably much less, 

 while, as a heat-producer, fat is worth about 2.-25 times as much as 

 protein. These facts, combined with the high cost of protein in foods, 

 render it usually uneconomical to feed protein for the production of 

 fat to be either stored in the body as such, or to be used as fuel, since 

 the fats and carbohydrates perform these offices, and cost mucli less. 

 It is to be remembered that the protein bodies are the "flesh formers," 

 and though they can perform the offices of fats and carbohydrates 

 in nutrition, fats and carbohydrates cannot take the place of protein. 



Fats and carboliydrates perform the same offices in the body — those 

 of the production of heat to keep the body warm, and the force by 

 which the animal mechanism is run. They are the "heat and force 

 producers," and are consumed in the body as fuel, giving out heat, 

 muscular and intellectual energy. For the production of heat and 

 energy one pound of fat is worth about 2.25 times as much as a 

 pound of carbohydrates. Fats give out about 2.25 times the heat 

 that carbohydrates do. Besides serving as heat and force producers, 

 carbohydrates are converted in the animal body into fats, and, 

 together with the fats of the food, are stored as such in fatty tissue. 

 The value of carbohydrates for the production of fats is supposed to 

 be in about the same proportion as the heat-producing powers of car- 

 bohydrates to fats. 



Carbohydrates are not found in the animal body as such, but are 

 converted into fats. There are, therefore, only four classes of sub- 

 stances composing the animal body, viz. : water, ash, fats and protein. 



The main and distinctive offices of the nutrients of foods are : 



Ash, or mineral constituents, are bone producers ; the protein bodies 

 are the flesh formers; and fats and carbohydrates are the heat and 

 force producers. The nutrients already located in the animal body 

 perform the same offices as the corresponding ones of foods. In case 

 of a deficiency of nutrients in foods given, the fats, or protein and 

 fats, are drawn upon to assist in running the animal machine. Car- 

 bohydrates and fats, in being consumed, prevent the consumption of 

 protein, but so soon as they become insufficient to supply the neces- 

 sary heat and force for the body, protein substance, in the form of 

 lean meat, muscle, etc., are drawn upon. A sufficient supply of car- 

 bohydrates and fats is, therefore, necessary to the protection t)f the 

 animal frame-work. The following, is a statement of the 



