Physics of the Hen's Egg Ii. the Bursting Strength of the Vitelline Membrane

It is almost certain that the strength of the membrane in an egg varies with the physiological factors of breed and diet of the hen. In an attempt to make this factor as constant as possible eggs from one farm and one breed of hen (White Leghorn) were used. Further, in order to counter obvious criticism, it was considered desirable to work with the intact membrane rather than with pieces of membrane. The method chosen was a hydrostatic one and the apparatus is shown diagrammatically in Fig. 1. The yolk, freed from white, is placed in an isotonic solution of sucrose with the surface remote from the germinal disc uppermost. The tube A (open at both ends) is then placed on the yolk and gradually lowered into the solution. In some of the experiments tube A was attached to a rachet; in others tube A was fixed and the sugar solution raised by means of a worm-gear. On top of the yolk, inside tube A, is placed a little sucrose solution to keep the exposed surface of the yolk moist. Tube A is lowered at a constant rate, approximately 1 cm. per min., and measurements made of the heights shown in Fig. 1. If 7\ and Tt are the tensions in the yolk membrane at the highest and lowest points, rx and r% are the radii of curvature at these points and p, and p, are the densities of yolk and sugar respectively then it can readily be shown that the following equation should apply: