Eggs are a specially interesting food because they contain all the elements necessary to the development of the young chick within the shell. The structure of the egg is familiar, with its division into the yolk and white, and it is interesting to note the details of this structure.
Break a fresh egg carefully into a saucer. The shell is porous, allowing water to evaporate from the egg and air to enter. To this porosity is due the fact that other sub-stances may enter the egg, giving it an unnatural flavor and even hastening its deterioration. Within the shell is a fine membrane which protects the white. The yolk is also divided from the white by a more delicate membrane which enables one to separate the yolk from the white of a fresh egg. A careful examination reveals at each end of the yolk a continuation of this membrane in the form of small cords which are fastened at each end of the shell, holding the yolk evenly suspended in the center of the shell. Rough handling or jolting breaks this membrane, and the yolk drops to one side.
Lift the white carefully with a fork, and notice its elasticity. This cohesive property makes it possible to beat air into the white until the whole mass become porous. The yolk is creamy rather than light when beaten, and a bit of the yolk mixed with the white prevents the latter from becoming light and dry.