HOW TO CANDLE EGGS. 
however, the contents shrink and the two membranes separate at the 
large end of the egg, forming an air space less than three-quarters 
of an inch in diameter. The outer or shell membrane follows the 
outline of the shell and is both tougher and thicker than the inner 
or egg membrane, which follows the outline of the egg contents. 
The shell of the egg is porous and varies in color from white to 
dark brown, depending upon the breed of the hen laying it. The 
yolk is composed mainly of fat, protein, and water; the white, of 
protein and water. The yolk sac, shell membrane, and fibers in the 
Avhite are made of keratin, a material similar chemically to finger 
nails or the horns or hoofs of animals. The shell is principally 
carbonate of lime. 
, Germ in a l.'sp o/' 
Thin wbiie •—-. 
Cha/aja. ~~^__ 
~ — '■— -~- H < • V ; - - 
Thick white - 
Thin -wh/'J-e. —- 
,'Yo/k 
Vo/k 
membrane. 
Cba/aja 
> ; ^ ffi^ ^99 'membrane. 
-.- -""-^ She// [ membrane^ 
She// 
Fig. 4. — Structure of an egg, 
HOW TO HOLD AN EGG WHEN CANDLING. 
The room in which the candling is done must be dark. The egg 
is held by hand in a slanting position with the large end against 
the opening in the candle. A few moderately rapid twists are given 
to the right and to the left. During this turning, which should be 
enough to expose the entire surface of the egg to view, the size of 
the air cell and the condition of the white and yolk should be noted. 
After this movement the egg should be turned from end to end so 
that the whole of the egg is again seen. If the egg is not completely 
turned before the candle bad eggs, such as those containing mold 
spots or yolks stuck to the shell, may not be detected. In other 
words, one side of an egg may appear good on candling, but the 
other side may be found to be bad if brought into view. 
It is customary to pick up two eggs in each hand, supporting one 
egg at a time in the tips of the thumb and the first two fingers (see 
fig. 2). Each egg should be candled separately. After the foremost 
egg in each hand has been candled, it is dropped back into the palm 
