Some Physical Properties of the Egg Shell Membranes in Relation to Their Resistance to Bacterial Penetration

THE inner shell membrane is a far more important barrier to bacterial penetration of the egg than is the outer membrane as shown by previous work done in this laboratory (Lifshitz et ah, 1964). Studies by many workers (Walden et al., 1956; Stokes and Osborne, 1956; Elliott and Brandt, 1957; and Garibaldi and Stokes, 1958) have shown that the membranes contain no bactericidal agent. The resistance of these structures to bacterial passage has been explained as mechanical. In the work reported here some mechanical properties of the membranes, namely weight, thickness and density, were compared in an attempt to account for their difference in resisting bacterial penetration. Eggs from one strain of Single Comb White Leghorns were used within 24 hours of lay. A circular area of two centimeters in diameter was removed from the small end of the egg and the contents discarded. The shell was washed…