378 Animal Husbandry 
wall of the poultry house, resting on the floor of the pen or ona 
platform 1 foot above the floor and 18 inches wide. The tin is bent 
and securely fastened to the side of the wall and to the platform. 
50. SrrucTuRE oF THE Eee 
Object. To study the structure of an egg. 
Materials. One lens, and facilities for boiling eggs. Hach 
pupil should be supplied with two eggs, if possible, one with a 
light shell, the other with a dark shell; two saucers; one drawing 
pencil; one box of colored lead-pencils ; a knife. 
An egg-tester can be made by placing a lamp in a box with a 
hole, slightly smaller than the egg, cut through the side. Or, the 
egg may be held up to a similar hole in the curtain of a darkened 
room. In either case, look through the egg toward the light. 
1. Strength of the egg shell. — Let the student hold a hard-shelled 
egg between the clasped hands, the ends of the egg in the hollow 
of the hand, and try to break it. 
Observe the great strength of the shell, due to the arrangement 
of the particles in an arch similar to the stones or bricks in the 
arch of a bridge. 
2. The contents of an uncooked egg. — (a) Break a fresh, uncooked 
egg in a saucer by separating the shell in the middle. 
Observe the ‘germinal disk,’’ which appears as a light-colored 
spot usually to be found on the upper surface of the yolk. 
The germinal disk contains the life principle of the egg. Being 
on the upper surface, it remains in close contact with the source 
of heat during natural incubation. 
(b) Note the “ chalaza,”’ or the whitish cords of denser albu- 
men on the sides of the yolk toward either end of the egg. These 
cords of denser albumen serve to keep the yolk properly suspended 
within the albumen. Thus the chick, which develops on the upper 
surface of the yolk, is protected from injury, if, through rough 
handling, it should come in contact with the shell. 
