DIETETICS 153 







doubt it is used over and over again. Milk is poor in iron, so 

 that if the child is weaned too late it is apt to become anemic, 

 and then the milk should be supplemented with food, like 

 the yolk of egg, which is rich in iron. The yolk of egg contains 

 an iron-holding nucleo-albumin called hematogen. 



Body Equilibrium. Just as it is possible to speak of 

 nitrogen or carbon equilibrium, it is possible to speak of water 

 equilibrium, oxygen and hydrogen equilibrium, salts equilib- 

 rium, etc. An adult under normal conditions lives so that 

 his ingesta are balanced by corresponding excretions; he is 

 in general body equilibrium and maintains a practically con- 

 stant body weight. If an exact balance is drawn between 

 proteins, fats, and carbohydrates eaten and those destroyed 

 in the body and represented by the nitrogen and carbon in 

 the excreta, we have a complete balance experiment. In 

 determining protein metabolism the nitrogen of the excreta 

 is multiplied by 6.25. The figure 6.25 is obtained from the 

 proportion, protein molecule : nitrogen contained : : 100 : 16. 

 That is, the nitrogen in the protein forms about 16 per cent, 

 of the molecule by weight. 



When, in addition to the determination of nitrogen, the 

 total quantity of carbon metabolism is desired, it is necessary 

 to place the individual in a specially constructed chamber, 

 or respiration apparatus, through which air is drawn by means 

 of a pump. The total quantity of air passing through is meas- 

 ured by a gasometer, and from time to time definite fractions 

 of air are drawn off and analyzed for carbon dioxide. Knowing 

 the total nitrogen and carbon eliminated, it is possible to esti- 

 mate the amount of protein, carbohydrate, and fat destroyed 

 in the body. A further refinement of this method has led to 

 the construction of respiration chambers in which the income 

 and outgo of energy are determined as well as the material 

 income and outgo. Such chambers act as calorimeters, so that 

 the total heat given off can be determined. The heat value 

 of the diet being known, it is possible to determine whether 

 or not the theoretical amount of heat is actually given off from 

 the body. 



Dietetics. This subject treats of the proper nourish- 

 ment of individuals or collections of individuals in health and 

 in sickness. The facts may be derived by study along two 



