A HEN’S EGG 211 
in the direction of the long axis, that it is able to with- 
stand a considerable force without breaking. The shell 
must be sufficiently strong to bear the weight of the 
bird, and sufficiently brittle to allow the chick to break 
through. 
Contents of the Egg.—The shell is lined with a thin 
white membrane—the shell membrane—which at the 
broad end is double, enclosing the air space or air 
chamber. The freshness of an egg is sometimes tested 
by holding it up to the light. If at the broad end a 
translucent space is seen, the egg is not fresh, for it has 
Gerrunal Disc 
Balancer 
< Albumen or Waite 
Fig. 124.—Section through egg Fig. 125.—_Diagrammatic view of a 
showing fiask-shaped mass or germ. Hen’s egg showing germinal disc. 
been laid sufficiently long to allow of the evaporation of 
some of the contents and the access of air which fills the 
air chamber. In a newly-laid egg the double membrane 
at the broad end is forced against the shell so that there 
is no air chamber. 
Inside the shell membrane are the albumen or white 
and the yolk. ‘The albumen is a clear, sticky and viscous 
fluid, which becomes solid and opaque on being heated. 
Its innermost part—or that immediately surrounding the 
yoke—is thicker than the rest, and is prolonged into 
two twisted cords the balancers, which gradually merge 
into the rest of the white and suspend the yolk in 
position. 
