EGGS AND THEIR VALUE AS FOOD. 7 



yolk and two-thirds in the white. The most abundant nutrient is 

 protein or nitrogenous matter, of which three-fifths of the total 

 is present in the white and two-fifths in the yolk. Protein supplies 

 nitrogen needed to build and repair the body tissue, and also some 

 energy, being equal to carbohydrate in this respect, although inferior 

 to fat, as noted on page 9. 



It is sometimes convenient to consider the relations of protein and 

 energy in a definite amount of foodstuffs. In the case of a whole 

 egg, 2.4 ounces of the edible portion would be required to supply 100 

 calories of energy, of which the protein would contribute 36 calories. 

 Of white, 6.9 ounces would be needed to supply 100»calories, and of 

 this amount 97 calories would be contributed by protein. In case 

 of the yolk, 1 ounce will supply 100 calories, of which protein con- 

 tributes 17. 



Mineral matter is required by the body for building bone and other 

 tissue and for regulating the body processes. In addition, recent 

 research has shown that certain accessory substances (so-called vi- 

 tamins, for example) are also present, which are required by the 

 body in at least minute amounts. Since eggs contribute to all these 

 body needs, their value as food is evident. 



In composition eggs resemble such animal foods as meat, milk, 

 and cheese, more than such vegetable foods as flour and potatoes. 

 As will be seen by the figures in the above table, hens' eggs and those 

 of other poultry do not differ greatly in composition. Furthermore, 

 there is practically no significant difference in composition between 

 hens' eggs with dark shells and those with white shells, although 

 there is a popular belief in some localities that the former are richer. 

 Neither does the cooked egg vary materially in composition from the 

 raw, though it varies markedly in texture. The yolk and the white, 

 on the other hand, differ greatly in composition, the yolk containing 

 considerable fat and ash, and the white being practically free from 

 fat and containing somewhat less protein and ash and considerably 

 more water than the yolk. Though both yolk and white, when raw, 

 are fluid, they are not thought of as containing water any more than 

 other familiar foods in which water is not visible as such but com- 

 bined or mingled with the other constituents so that the whole food 

 is more or less moist, liquid, or juicy. This and similar facts are 

 brought out in figure 1, which shows in diagrammatic form the com- 

 position of eggs and egg products. 



Though eggs are conceded to be a nutritious food, they are less 

 concentrated, that is, they contain more water than some — cheese, 

 for instance. On the other hand, they are more concentrated than 

 many others, milk or oysters, for instance, and on the whole do not 

 differ greatly in this respect from lean meat. Their general resem- 

 blance in composition to other common animal foods suggests that 



