EGGS AND TIE HEN 331 
and others 134 ounces or less. An egg consists of four 
parts—the outer covering or shell, the yolk or food sup- 
ply of the chick at hatching, the white, or mass of albu- 
men for developing the embryo, and the germ, or life sub- 
stance. The white material comprises about 60 per cent 
of the entire egg, the yolk about 30 per cent and the shell 
about 10 per cent. 
3. Egg shells.—The outer covering of an egg is some- 
times brown and sometimes white, the color depending 
in a large measure on the breed 
or variety of the hen. Color is 
due to a pigment developed in 
the shell and is a fixed character 
of the breed. The shell is com- 
posed of carbonate of lime, 
Bets Suowine Good Sue ano phosphate of lime, and atumal 
L 
gluten. It is very porous. It 
has between the particles of lime an innumerable number 
of very small holes, which allow the air to pass freely 
backward and forward during the process of incubation. 
If it were not for these tiny holes the embryo within 
would die for want of oxygen to revive the 
impure blood that it produces. ‘ar 
Moisture is evaporated through these holes. The 
rapidity will depend on the conditions and the 
temperature under which the egg is kept. The air 
space at the broad end of the egg indicates the 
amount that has been evaporated. The longer an 
egg is kept the larger the air space becomes. This 
is one way to tell the age of an egg. Ecc SHowinc EN- 
4, White of an egg.—The white of an AIR SPACE UP 
egg is a strong solution of albumen in Up enat 
water, and while readily mixable with water in its ordi- 
nary state, it becomes insoluble when subjected to heat. 
In 100 parts, the white consists of 80 of water, 1514 of 
