18 THE DEVELOPMENT OF THE CHICK 
The shell-membrane consists of two layers, a thick outer 
layer next to the shell and a thinner one next the albumen. Both 
are composed of matted organic fibers (more delicate in the inner 
than in the outer layer), crossing one another in all directions. 
At the blunt end of the ege the two layers are separated and 
form a chamber containing air that enters after the egg is laid 
(Fig. 2). 
The physical characteristics of the albumen are too well 
known to require description. A dense layer immediately next 
Bf LVLs 
Fig. 2. Diagram of the hen’s egg in section to show relations of the parts. 
A. C., Air chamber. Alb., Albumen. BI., Blastoderm. Chal., Chalaza. 
[. S. M., Inner layer of the shell membrane. L., Latebra. N. L., Neck of 
Latebra. N.P., Nucleus of Pander. O.S. M.. Outer shell membrane. Dp Vass 
Perivitelline space. S., Shell. V.M., Vitelline membrane. W. Y., White 
yolk. Y. Y., Yellow yolk. 
to the vitelline membrane is prolonged in the form of two spirally 
coiled opalescent cords towards the blunt and narrow ends of 
the egg respectively; these are the chalaze, so called from a 
fanciful resemblance to hail stones. The two chalaze are twisted 
in Opposite directions. In a hard-boiled egg it is possible to strip 
off the albumen in concentric spiral layers from left to right from 
the broad to the small end of the ege. 
