In vivo O2 and water vapor permeability of the hen's eggshell during early development.

The area of the chorioallantois was measured from the time it makes contact with the eggshell membranes on day 6 until it has completely enveloped the egg content on day 12. The oxygen uptake and air cell O2 tension were also determined during this period. These observations allow one to calculate that the O2 flux is confined to those areas of the shell which cover the chorioallantois and that the O2 permeability of the shell (including the outer membrane), KO2, is constant. The water vapor permeability of the shell, KH2O, was also measured. Since the ratio of KH2O/KO2 is essentially equal to the ratio of their diffusion coefficients, DH2O/DO2, it suggests a common diffusion path for O2 and water molecules.