(3) The firm or thick layer of albumen provides an envelope or jacket which
holds the inner, thin white and the yolk. It adheres to the shell membrane at each end
of the egg. Approximately 55 percent of the white is firm albumen.
(4) The outer, thin layer lies just inside the shell membranes, except where
the thick white is attached to the shell, and accounts for about 21 percent of the total
b. It is in the oviduct that the white, shell membranes, and shell are secreted.
(1) In the first part of the oviduct, which is the infundibulum, the yolk is
engulfed and started on its way down the oviduct. The yolk moves through the
infundibulum to the magnum in about 15 minutes.
(2) In the magnum area is secreted the thick white, which comprises
approximately 55 percent of the albumen and practically all the protein in the albumen.
The quality of the white is largely dependent on the amount of mucin secreted by this
part of the oviduct.
(a) The albumen (see figure 1-2) secreted by the magnum is a
homogeneous gel. The mucin (secreted as fibers) is responsible for the gel. The
portion of the gel immediately adjacent to the yolk undergoes partial liquefaction before
the egg leaves the magnum. The spiral movement of the developing egg as it passes
through the oviduct causes the mucin fibers to draw together.
(b) From these strands, the chalaziferous layer and the chalazae are
formed. The twisting and drawing together of these mucin strands tend to squeeze out
thin albumen to form the inner, thin white. Thus, three layers of albumen are formed
from the homogeneous gel as follows: (1) chalaziferous layer continuous with the
chalazae, (2) the inner thin white, and (3) the thick white. The outer, thin white (4th
layer) is added in the uterus through the shell membranes. The water and solids
content of the white ultimately becomes equally distributed in the various layers of the
The time required for the yolk to travel through the magnum is
about 3 hours.
(3) In the isthmus, some water and mineral salts are added and the two
shell membranes are deposited. The developing egg passes through this area in about
1 1/4 hours.
(4) In the uterus, the thin white, the hard shell, and the cuticle of the
completed egg are formed. The thin white is secreted in the anterior portion of the
uterus and is called "plumping" the egg. The posterior portion of the uterus deposits