The hen's egg: Some factors affecting deformation in statically loaded shells

Synopsis

Experiments are described from which it was established that when a hen's egg shell is loaded statically with a load that does not cause fracture,

1. deformation of the shell occurs almost entirely in the close vicinity of the points at which the load is applied;

2. a small amount of deformation occurs over the shell as a whole;

3. most of the variance of the deformation is associated with variation in R_xRy/(R_x+R_y) T² _e for the loading points, where R_x and R_y are the radii of principal curvature and T² _e, the local effective thickness of the shell, is equal to the estimated local mean thickness of the mineral moiety;

4. part of the residual variance is associated with variation in

   for polar and equatorial loading respectively, where B is the maximum breadth of the egg, L its length, X‘_m the distance from the plane of maximum width to the broad pole and T_e the mean effective thickness of the shell;

5. a small part of the residual variance is associated with variation in pore density near the loading points;

6. a small part of the residual variance is due to between‐hen differences that may be mediated through roughness of the shell's surface at the loading points.

The residual variance was unaffected by variation in position of the egg in the clutch and organic content of the shell. There was no convincing evidence of genetic variation in shell material “ quality “.