A morphological study on the shell-membrane of the chicken egg was performed in the course of developement by the use of a scanning electron microscope and the silver impregnation method.
The shell membrane began to form at the beginning of the isthmus by the formation of a coarse meshwork of fine fibers. Fine fibers were cemented with one another by mucin-like material to form a meshwork which became the inner layer of the inner shell membrane. Then relatively large fibers were added to the already formed meshwork of fibers of the inner layer in the middle portion of the isthmus. They developed into the outer layer of the inner shell membrane. Very large fibers were added to the inner shell membrane in the end portion of the isthmus. They developed into the outer shell membrane. The formation of the shell membrane was accomplished just before eggs descended to the uterus.
The shell membrane of the fully formed egg was divided into three layers, the inner and the outer layer of the inner shell membrane and the single layer of the outer shell membrane. The inner layer of the inner shell membrane is a thin layer adjoining directly to albumen. It is a mucin-like layer containing fine fibers. The outer layer of the inner shell membrane is formed by a meshwork of fibers about 2µ in diameter. These fibers are characterized by the presence of granular concretions around each fiber. The outer shell membrane is formed by a coarse meshwork of fibers 3-4µ in width. These fibers are combined with one another in such manner as to form knots.